,transcriber's ,notes      ,text printed
 in italics has been transcribed between
 underscores1    bold face text between 
equal signs4 ,text between tildes       
represents    blackletter text1 text    
represents superscript text4 ,small     
capitals    have been replaced with     
,,all ,,capitals4      ,more            
,transcriber's ,notes may be found at   
the end of this text4                   
,illustration3 ,pl4 ,,ii4    ,accums'1  
,description of ,gas ,works4    to ,face
 ,title4    ,mulholland ,delt4    ,w4   
,read1 ,sculpt4 ,maiden ,lane1 ,covent  
,garden4    ,,gas ,,light ,,apparatus1  
,erected by ,order of ,government at    
,,the ,,royal ,,mint1 by ,fredck4       
,accum4            ,,description    ,,of
    ,,the ,,process ,,of ,,manufacturing
    ,,coal ,,gas1    ,,for ,,the        
,,lighting ,,of ,,streets ,,houses1     
,,and ,,public ,,buildings1    ,,with   
,,elevations1 ,,sections1 ,,and ,,plans 
,,of ,,the ,,most ,,improved ,,sorts    
,,of ,,apparatus    ,,now ,,employed    

,,at ,,the    ,gas ,works in ,london1   
,,and ,,the ,,principal ,,provincial    
,,towns ,,of ,,great ,,britain2         
,accompanied with comparative           
,estimates1 exhibiting the most         
,economical ,mode of procuring this     
species of ,light4      ,illustration3  
,plate ,i4      ,,with ,,seven ,,plates4
      ,,by ,,fredrick ,,accum1          
,,operative ,,chemist1      ,lecturer on
 ,practical ,chemistry1 on ,mineralogy1 
and on ,chemistry    applied to the     
,arts and ,manufactures2 ,member o the  
,royal ,irish    ,academy1 ,fellow of   
the ,limnan ,society1 ,member of the    
,royal ,academy of    ,sciences of      
,berlin1 c4 c4      ,london4            
,,printed ,,for ,,thomas ,,boys4 ,no4   
#g4 ,,ludgate-,,hill4 7,,from ,no4 #c1  
,,paternoster ,,row7      ,,mdcccxix4   
,,preface4        ,compton ,street1     
,soho4    ,the extraordinarily rapid    
progress which the recent invention of  
lighting with coal gas has made in this 
country1 is perhaps without a  parallel 

in the history of the useful arts4      
,it was an invention not exempted from  
the misfortune common to all            
innovations on established practises1 of
 encountering opposition1 but it  had   
the fortune common to few1 of obtaining 
an almost instantaneous  triumph4    ,a 
single exhibition of the gas lights in  
actual use was sufficient to  determine 
the public judgment in favour of the new
 mode of illumination2  to see was in   
this case1 indeed to believe4    ,the   
legislature responsive to the popular   
voice1 and fortified in its             
responsibility1 by the results of       
special enquiries which were ordered  to
 be made into the merits of the         
invention1 and in which ,i had the good 
fortune to be professionally engaged1   
gave the most liberal and decided       
encouragement to its adoption4          
,capital1 often wanting even in this    
opulent country for undertakings of     
magnitude1 came to the promotion of the 
new art of procuring and  distributing  

light in overflowing abundance2 and     
already ere many years  are elapsed1    
such has been the rapidity with which   
the gas light  illumination has         
advanced1 that there is not a city and  
scarcely a town  of any note in ,great  
,britain1 in which the art of lighting  
by means of  gas1 has not been carried  
into effect1 or in which active measures
 are  not in progress1 to participate in
 the benefit of this important          
discovery4    ,when the art was yet in  
its infancy1 ,i published a ,treatise1  
containing  a description of the        
apparatus and machinery best calculated 
for  illuminating streets1 houses1 and  
public buildings1 by means of coal  gas1
 with remarks on the utility1 safety1   
and general nature of this new  branch  
of domestic economy1 as far as then     
understood1 and practised in  the       
metropolis4    ,the universal avidity   
for information on the subject1 more    
perhaps than  any particular merit in   
the work itself1 produced a demand in   

this  country for four large impressions
 of this work1 in the course of a few   
years1 and ,i have also had the         
satisfaction of finding that the        
,treatise  has been translated into the 
,french1 ,german1 and ,italian          
languages4    ,since this work was      
written1 however1 the art of            
manufacturing and  applying coal gas1   
has undergone so many material          
improvements1 all  combining to bring it
 to a degree of simplicity1 precision1  
and economy1  far surpassing every thing
 which the original mode of practice    
exhibited1 that ,i have felt ,i should  
be guilty of an injustice to the        
constant demand which still exists for  
my former ,treatise1 had ,i not  made it
 my duty to publish the work ,i now     
present to the reader2  superseding     
altogether the former publication1 but  
superseding it from  circumstances of   
necessity1 and with a view to good1     
which ,i trust will  be found not       
illusory4    ,the present treatise1 as  

its title expresses1 is intended to     
exhibit the  superior process of        
manufacturing coal gas now employed in  
the  metropolis and the provincial towns
 of ,great ,britain1 and to lay before  
the reader the elevations1 sections1 and
 plans of the improved ,gas ,light      
machinery1 which has stood the test of  
practice1 and is now in action at  the  
most celebrated ,gas ,light             
,establishments4    ,in the first and   
second part of the ,treatise1 ,i have1  
as introductory  to the rest1 given a   
sketch of the chemical theory and       
production of ,gas  ,light4 ,i have     
pointed out the leading objects of      
public and private  utility1 to which   
the art of lighting with gas has been1  
or remains to  be applied3 and added    
such other facts and observations as may
 serve to  remove all doubt in the minds
 of the reader as to the important      
benefit  which this country in          
particular1 and the world at large1 have
 gained by  this discovery4    ,in the  

third part ,i have stated the maximum   
quantities of gas obtainable  in the    
large way1 from different kinds of coal4
    ,in the fourth part1 ,i have given a
 description of all the various forms   
and dimensions which the distillatory   
vessels or retorts have  successively   
assumed1 as well as of the improvements 
that have been made  in the mode of     
setting the retorts1 with a view to     
saving them from  undue deterioration1  
and preventing any improvident waste of 
fuel4 ,i  have here given a particular  
account of the distillatory apparatus   
now  used at the most celebrated gas    
works in the metropolis4    ,the fifth  
and sixth parts1 lead the reader        
considerably further into a  knowledge  
of the economy and practice of this art4
 ,they contain an  account of a great   
variety of experiments which have been  
pursued on a  large scale1 in order to  
ascertain the most profitable mode of   
employing the retorts1 the differences  
of opinion which have existed  among    

practical men with respect to the degree
 of temperature fittest to  be applied1 
and the number of hours at a time during
 which the retorts  may most            
advantageously be kept in action1 with  
the particular results  which the       
experiments instituted into these points
 have afforded2 and  such other data1 as
 will enable the reader to adopt that   
mode of  operation1 which under every   
circumstance of locality will be found  
most  advantageous4    ,the changes     
which have taken place with respect to  
the retorts1 have  been before detailed 
in part fourth2 but in order to give the
  manufacturer a nearer insight into the
 superior advantages attending  retorts 
of the construction lately brought into 
use1 ,i have given in  part seventh1 a  
detailed description of the horizontal  
rotary retorts1  the application of     
which has led to a more economical1     
expeditious1 and  easy method of        
manufacturing coal gas than heretofore  
practised4 ,i have  distinctly pointed  

out the advantages which these retorts  
present1 the  particular results they   
afford1 and the method of applying them4
    ,the purification of coal gas forms 
the subject of part eighth4 ,i have     
compared here1 the apparatus for        
purifying coal gas1 as it was           
originally constructed1 with the        
improved machinery lately adopted1      
showing the inefficacy and defects of   
the former1 and the decided  superiority
 which belongs to the latter4    ,the   
ninth part gives an account of the      
various improved gas holders  which have
 been invented1 and now are in action at
 the most recent  establishments1 for   
the purpose of storing large quantities 
of gas4 ,the  improvements that have    
been made in this department of the ,gas
 ,light  machinery1 are particularly    
valuable and have contributed more      
perhaps  than any other1 to lessen the  
expence of manufacturing gas for        
commercial purposes4    ,in the tenth   
part1 ,i have given a description of an 

entirely new  machine1 called the       
gas-metre1 or self-acting guage1 lately 
adopted at  the ,birmingham1 ,chester1  
and other gas works1 which measures and 
registers the quantity of gas           
manufactured in any given time1 from any
  given quantity of coal1 or consumed   
during any period1 by any number of     
burners or lamps4 ,the great services   
which such a machine must render  both  
to the manufacturer and consumer of gas1
 are particularly pointed  out1 and     
illustrated to the manufacturer1 by     
serving as a complete check  on his     
workmen as to the quantity of work that 
ought to be performed1  and to the      
consumer1 as an exact measure of the    
quantity of gas he  receives1 and ought 
to pay for4    ,the eleventh part is    
appropriated to the description of      
another  apparatus1 called the governor1
 also of recent invention1 and now in   
use  at numerous establishments4 ,the   
design of this machine is1 to regulate  
the pressure of the gas1 before it      

enters into the mains1 the importance   
of which must be sufficiently manifest4 
,i have also pointed out the            
application of this apparatus for       
regulating the magnitude of the flames  
of gas burners and lamps4    ,the       
twelfth part treats on gas mains and    
branch pipes1 ,i have here  stated the  
rules and practical proceedings         
necessary to be observed1 for  applying 
and distributing gas pipes to the       
greatest advantage4    ,the most        
efficient method of introducing the gas 
to the interior of  houses1 forms the   
subject of part thirteen4 ,all the      
necessary  instructions are here given  
to workmen1 for adapting the gas pipes1 
and  insuring success at the least cost1
 under every variety of  circumstances4 
,the fourteenth part gives an account of
 the illuminating power of coal         
gas--the quantity of gas consumed in a  
given time1 by different kinds of  gas  
burners and lamps1 the relative cost of 
gas1 tallow1 and oil lights  of         

different intensities1 and the most     
improved method employed for            
ventilating apartments lighted by gas4  
,in the fifteenth and sixteenth parts1  
,i have added an account of the         
manufacture of carburetted hydrogen gas1
 from coal tar1 vegetable tar1  and oil1
 with such other observations as may    
enable the reader to form a  proper     
estimate of the comparative advantage of
 manufacturing gas from  oil1 or tar1   
under certain circumstances4 ,i have    
here also given an  account of the      
manufacture of carbonate of ammonia1 as 
now practised1  from the ammoniacal     
liquor obtained in the ,gas ,light      
process1 and of the  manufacture of     
other saleable products obtainable from 
coal1 namely2  pitch1 coal tar1 and oil4
    ,in conclusion ,i have to observe   
that my object throughout has been to   
make the work a compendium of all the   
best information which the  practice of 
the art down to the present moment has  
been able to afford1  embodying a great 

number of data1 with which ,i have been 
obligingly  favoured by gentlemen1 the  
most practically versant in the art1 and
 for  which ,i beg they will            
individually accept this public         
expression of my  thanks1 and           
obligations1 as well as the results     
which my own labours in  this           
department1 neither few1 nor            
inconsiderable have furnished4    ,to   
supply the reader with a work of        
practical utility in a most  valuable1  
and growing branch of national economy  
has been my object2 and  ,i need        
scarcely add1 that the suffrages of the 
public to the zeal and  industry at     
least with which ,i have endeavoured to 
obtain that object1  will be a source of
 infinite satisfaction4      ,,fredrick 
,,accum4      ,,london1 #ahai4          
,,contents4        ,,part ,i4           
,,page      ,,general ,,nature ,,and    
,,advantages ,,of ,,the ,,art ,,of      
,,procuring ,,light1 ,,by    ,,means    
,,of ,,carburetted ,,hydrogen1 ,,or     

,,coal ,,gas                            
#a        ,,part ,,ii4      ,,outline   
,,of ,,the ,,new ,,art ,,of ,,procuring 
,,light ,,by ,,means ,,of ,,coal ,,gas1 
,,and ,,theory ,,of ,,the ,,production  
,,of ,,gas ,,lights                     
#cc        ,,part ,,iii4                
,,classification ,,of ,,pit ,,coal1     
,,and ,,maximum ,,quantity ,,of ,,gas1  
,,obtainable ,,from ,,different ,,kinds 
,,of ,,coal                             
#da        ,,part ,,iv4      ,,form     
,,and ,,dimensions ,,of ,,the ,,retorts 
,,originally ,,employed ,,for           
,,manufacturing ,,coal ,,gas            
#ea      ,,application ,,of             
,,heat--,,flue ,,plan ,,originally      
,,adopted                   #ei         
,,report ,,on ,a ,,course ,,of          
,,operations1 ,,made ,,with ,,sets ,,of 
#ff1 ,,of #cj1 ,,of    #aaf1 ,,and ,,of 
#fd ,,retorts1 ,,worked ,,on ,,the      
,,flue ,,plan                     #fa   
,,oven ,,plan ,,lately ,,adopted        
#fg      ,,description ,,of ,,the       

,,retort ,,oven                         
#fi        ,,part ,v4      ,,difference 
,,in ,,the ,,quantity ,,of ,,gas        
,,evolved ,,during ,,different          
,,periods ,,of ,,the ,,distillatory     
,,process1 ,,and ,,economical           
,,considerations ,,resulting ,,therefrom
 ,,in ,,the ,,manufacture ,,of ,,coal   
,,gas   #gg      ,,experiments ,,with   
#ah ,,cylindrical ,,retorts1            
,,containing ,,one ,,chaldron    ,,of   
,,coal                                  
#hj      ,,experiment ,,with            
,,thirty-,,six ,,parallelopipedal       
,,retorts1 ,,each    ,,containing ,,two 
,,bushels ,,of ,,coal                   
#ha      ,,report ,,on ,a ,,course ,,of 
,,experiments ,,made ,,to ,,ascertain   
,,the    ,,comparative ,,economy ,,of   
,,manufacturing ,,every ,,week1 #heg1ffg
 ,,cubic    ,,feet ,,of ,,gas1 ,,by     
,,means ,,of ,,cylindrical ,,retorts    
,,variously ,,worked       #hd          
,,part ,,vi4      ,,temperature ,,best  
,,adapted ,,for ,,working ,,cylindrical 

,,retorts            #id      ,,annual  
,,creditor ,,and ,,debtor ,,account ,,of
 ,,manufacturing ,,daily1 ,,from        
#ej1jjj ,,to #ajb1jjj ,,cubic ,,feet    
,,of ,,gas1 ,,at ,,the ,,price ,,which  
,,coal    ,,bears ,,in ,,the            
,,metropolis1 ,,the ,,operation ,,being 
,,commenced ,,with ,,new    ,,retorts1  
,,and ,,the ,,retorts ,,being ,,left    
,,in ,a ,,fit ,,working ,,state         
#ig      ,,comparative ,,facility ,,with
 ,,which ,,the ,,decomposition ,,of     
,,different    ,,species ,,of ,,coal    
,,is ,,effected                         
#ajf        ,,part ,,vii4               
,,horizontal ,,rotary ,,retorts1        
,,lately ,,brought ,,into ,,use ,,for   
,,manufacturing ,,coal ,,gas            
#aaj      ,,description ,,of ,,the      
,,horizontal ,,rotary ,,retorts ,,at    
,,the ,,royal ,,mint     #aab           
,,action ,,and ,,management ,,of ,,the  
,,horizontal ,,rotary ,,retorts         
#abj      ,,advantages ,,of ,,the       
,,method ,,of ,,manufacturing ,,coal    

,,gas ,,by ,,means ,,of    ,,horizontal 
,,rotary ,,retorts                      
#abd      ,,directions ,,to ,,workmen   
,,with ,,regard ,,to ,,the ,,management 
,,of ,,horizontal    ,,rotary ,,retorts 
#acd        ,,part ,,viii4              
,,purifying ,,apparatus1 ,,or ,,lime    
,,machine                               
#adj      ,,lime ,,machine ,,originally 
,,employed ,,for ,,the ,,purification   
,,of ,,coal ,,gas  #ada      ,,lime     
,,machine ,,lately ,,adopted            
#adi      ,,test ,,apparatus1 ,,for     
,,certifying ,,the ,,purity ,,of ,,coal 
,,gas1 ,,and ,,the    ,,proper ,,manner 
,,of ,,working ,,the ,,lime ,,machine   
#aeg      ,,best ,,method ,,of          
,,preparing ,,quick-,,lime ,,for ,,the  
,,purification ,,of ,,coal    ,,gas     
#afa        ,,part ,,ix4      ,,gas     
,,holder                                
#afd      ,,gas ,,holder ,,as           
,,originally ,,employed                 
#afe      ,,gas ,,holder ,,with         
,,governor1 ,,or ,,regulating ,,guage1  

,,lately ,,brought    ,,into ,,use      
#afi      ,,gas ,,holder ,,with         
,,governor ,,or ,,regulating ,,guage    
,,at ,,the ,,chester ,,gas    ,,works   
#age      ,,gas ,,holder ,,with         
,,governor ,,or ,,regulating ,,guage    
,,at ,,the ,,birmingham    ,,gas ,,works
                                        
#agg      ,,revolving ,,gas ,,holder    
,,at ,,the ,,westminster ,,gas ,,works  
#aha      ,,rule ,,for ,,finding ,,the  
,,capacity ,,of ,a ,,revolving ,,gas    
,,holder ,,of ,,given    ,,dimensions   
#ahe      ,,collapsing ,,gas ,,holder   
#ahe      ,,rule ,,for ,,finding ,,the  
,,capacity ,,of ,a ,,collapsing ,,gas   
,,holder ,,of ,,given    ,,dimensions   
#aie      ,,reciprocating ,,safety      
,,valve                                 
#aif        ,,part ,x4      ,,gas       
,,metre1 ,,or ,,self-,,acting ,,guage1  
,,which ,,measures ,,and ,,registers1   
,,in    ,,the ,,absence ,,of ,,the      
,,observer1 ,,the ,,quantity ,,of ,,gas 
,,produced ,,in ,a    ,,given ,,time1   

,,from ,,any ,,given ,,quantity ,,of    
,,coal1 ,,or ,,consumed ,,during ,a     
,,given ,,period1 ,,by ,,any ,,number   
,,of ,,burners ,,or ,,lamps             
#bjj      ,,description ,,of ,,the ,,gas
 ,,metre ,,at ,,the ,,royal ,,mint ,,gas
 ,,works           #bad      ,,rule     
,,for ,,calculating ,,the ,,weight1     
,,which ,a ,,gas ,,metre ,,of ,,given   
,,dimensions1 ,,will ,,raise1 ,,to ,a   
,,given ,,height1 ,,in ,a ,,given ,,time
         #bbj      ,,gas ,,holder       
,,valve                                 
#bba      ,,siphon1 ,,or ,,water        
,,reservoir                             
#bba        ,,part ,,xi4      ,,governor
 ,,or ,,regulating ,,guage              
#bbe      ,,directions ,,to ,,workmen   
,,for ,,fixing ,,the ,,governor ,,and   
,,gas ,,metre        #bbi        ,,part 
,,xii4      ,,gas ,,mains ,,and ,,branch
 ,,pipes                                
#bci      ,,weight ,,of ,,cast ,,iron   
,,gas ,,mains ,,of ,,different ,,lengths
 ,,and ,,bores       #bea        ,,part 

,,xiii4      ,,gas ,,lamps ,,and        
,,burners                               
#bec      ,,directions ,,to ,,workmen1  
,,for ,,adapting ,,gas ,,pipes ,,to     
,,the ,,interior ,,of    ,,houses       
#beh        ,,part ,,xiv4               
,,illuminating ,,power ,,of ,,coal      
,,gas1 ,,and ,,quantity ,,of ,,gas      
,,consumed ,,in ,a    ,,given ,,time1   
,,by ,,different ,,kinds ,,of ,,burners1
 ,,and ,,gas ,,lamps           #bfi     
,,part ,,xv4      ,,gas ,,from ,,coal   
,,tar                                   
#bhb      ,,gas ,,from ,,oil            
#bhi        ,,part ,,xvi4      ,,other  
,,products ,,obtainable ,,from ,,coal1  
,,namely3      ,,coal ,,tar             
#bih      ,,coal ,,oil                  
#cjj      ,,pitch                       
#cjb      ,,ammoniacal ,,liquor         
#cjc      ,,manufacture ,,of ,,carbonate
 ,,of ,,ammonia ,,from ,,the            
,,ammoniacal ,,liquor     #cjc          
,,manufacture ,,of ,,muriate ,,of       
,,ammonia ,,from ,,the ,,ammoniacal     

,,liquor       #cjg      ,,description  
,,of ,,the ,,plates                     
#cae      ,,index ,,to ,,the ,,work     
#cba      ,,london ,,price ,,list ,,of  
,,the ,,most ,,essential ,,articles     
,,employed ,,in ,,the    ,,manufacture  
,,and ,,application ,,of ,,coal ,,gas   
#cca          ,,advertisement4          
,the author of this work respectfully   
informs the public1 that they may    be 
furnished with estimates1 and plans for 
the building of ,gas ,works1            
particularly adapted to the             
circumstances of the places where they  
are    to be established1 and that he   
proposes to superintend the erection of 
the works4      ,mr4 ,accum also engages
 to supply the whole of the ,gas        
,apparatus ready    for immediate use1  
and to guaranty its efficient           
performance4      ,or he will contract  
with any committee1 directory1 or public
 company1    for ,lighting with ,gas1   
any ,town1 ,manufactory1 or ,building1  
upon    whatever scale of magnitude1 for

 an annual specific sum4      ,of the   
qualifications for the services which he
 thus proffers1 he    would speak with  
diffidence4 ,such proofs as he is able  
to offer of    them1 are to be found in 
the work here laid before the reader1   
beyond    which he would add no more    
than the flattering testimony of        
approbation1 with which his labours have
 been honoured1 in having been          
selected by ,,his ,,majesty',s          
,,government to plan and erect the ,,gas
 ,,works    at the ,,royal ,,mint1 and  
since entrusted with the active         
management and    superintendance of    
that establishment4      ,compton       
,street1 ,soho1      ,may #bh1 #ahai4   
,the following particulars are required 
to be stated by those who are           
desirous of receiving estimates1        
concerning the comparative economy of   
applying coal gas as a substitute for   
oil1 wax1 or tallow light4      #a4 ,a  
plan of the place to be lighted with    
,gas1 drawn to a scale not    less than 

one tenth of an inch1 to ten feet4 ,the 
design must exhibit    the particular   
spot1 where the ,machinery is to be     
erected4      #b4 ,the kind of gas      
lights required1 namely2 whether the    
lights shall    be equal in illuminating
 power to one1 or more tallow candles of
 a    given weight1 or equal to an      
argand lamp4      #c4 ,the number of    
lights4      #d4 ,the average time the  
lights are to burn1 throughout the year4
      #e4 ,the average price of coal1   
and rate of workmen's wages1 at the     
place where the light is wanted4        
,,an    ,,account    ,,of ,,the         
,,process ,,of ,,manufacturing    ,coal 
,gas4          ,,part ,i4      ,general 
,nature and ,advantages of the art of   
procuring ,light1 by means  of          
,carburetted ,hydrogen1 or ,coal ,gas4  
,the new art of lighting houses1 streets
 and manufactories1 with  carburetted   
hydrogen1 or coal gas1 is one of those  
modern discoveries on  which the        
admirers of science and the inhabitants 

of this country in  particular1 have    
greater reason to congratulate          
themselves1 than any  other invention or
 discovery of the present age4    ,this 
art is so wonderful and important1 it   
speaks so forcibly by the  effects it   
has already produced1 that it cannot    
fail to increase the  wealth of the     
nation by adding to the number of       
internal resources1 as  long as coal    
continues to be dug in this island from 
the bowels of the  earth4    ,for if we 
distribute the catalogue of human wants 
which a civilized  state of society has 
introduced1 the production and supply of
 artificial  light1 holds next to food1 
clothing and fuel1 the most important   
place4  ,we might indeed exist without  
it1 but how large a portion of our lives
  would in that state be condemned to a 
state little superior in efficacy  to   
that of the animals around us4    ,if we
 could for a moment suppose the         
privation of artificial light1  during  
the absence of the ,sun1 it would follow

 as an immediate  consequence that the  
greatest part of the globe on which we  
dwell1 would  cease to be the habitation
 of man4 ,whether he could ensnare or   
overtake  those animals upon whose      
unprepared remains he would then be     
compelled  to feed2 whether he might    
store the fruits of the earth for his   
winter  supply--what might be the       
physical and moral consequences of a    
state of  such desolation1 may perhaps  
be conjectured1 but no estimate can show
  its dreadful magnitude4    ,how much  
do our comforts1 and how greatly does   
the extent of our power  depend upon the
 production and supply of artificial    
light4 ,the flame of  a single candle   
animates a family1 every one follows his
 occupation1 and  no dread is felt of   
the darkness of night4 ,it might be a   
curious  speculation to enquire how far1
 and in what respect1 the morals of men 
would become degraded by the want of    
this contrivance4 ,but it is  sufficient
 on the present occasion1 that1 previous

 to entering upon a  dissertation       
respecting a new art of procuring light1
 a train of ideas  has slightly been    
hinted at1 which cannot fail to show its
 magnitude and  importance4    ,the     
progress of the new art of lighting     
houses1 streets and public  buildings1  
by means of the inflammable gas         
obtainable from coal1 has  been within  
these few years uncommonly rapid4 ,the  
number of gas-lights  already in use in 
the metropolis alone1 amounts to upwards
 of fifty-one  thousand4 ,the total     
lengths of mains in the streets through 
which the  gas is conveyed from the     
gas-light manufactories into the houses1
 now  measures two hundred and          
eighty-eight miles4    ,the gas-light   
illumination has also spread far and    
wide through the  country4              
,establishments for the supply of the   
new lights are carried on  at           
,edinburgh1 ,glasgow1 ,liverpool1       
,bristol1 ,bath1 ,cheltenham1           
,birmingham1  ,leeds1 ,manchester1      

,exeter1 ,chester1 ,macclesfield1       
,preston1  ,kidderminster1 and in many  
other towns and places of ,great        
,britain4    ,every body is now         
convinced that pitcoal is capable of    
furnishing light  superior to that      
obtained from oil1 wax1 or tallow4 ,the 
public attention  is awakened to the new
 value of coal1 and will not rest till  
the art of  lighting with gas is pushed 
to the utmost of its extent4    ,in     
order to arrive at a full and accurate  
knowledge of the many  advantages       
attending the application of carburetted
 hydrogen or coal  gas1 as a substitute 
for candles or lamps1 it may be         
necessary1  especially for the          
information of those readers who have   
never  personally witnessed this mode of
 illumination1 to take a brief          
preliminary view of some of the leading 
objects of public and private  utility1 
to which this mode of procuring and     
distributing light may be  applied1 and 
of the extent to which it is entitled to

 national  encouragement4    ,the chief 
advantages attending the use of gas1 are
 superiority and  uniformity of light1  
saving of labour1 cleanliness1 safety   
and  cheapness4    ,it must be difficult
 for a person wholly unacquainted with  
this art1 to  imagine with what facility
 and neatness gas-lights are managed4   
,the gas  being collected in a          
reservoir1 is conveyed by means of      
tubes1 which  branch out into smaller   
ramifications1 until they terminate at  
the  places where the lights are wanted4
 ,the extremities of the branching      
tubes are furnished with burners1 having
 small apertures out of which  the gas  
issues with a certain velocity          
corresponding to its degree of          
pressure4 ,near the termination of each 
tube1 there is a stopcock1 or  valve1   
upon turning which when light is        
required1 the gas instantly  flows out  
in an equable stream4 ,there is no noise
 at the opening of the  valve1 no       
disturbance in the transparency of the  

atmosphere2 the gas  instantly bursts on
 the approach of a lighted taper into a 
peculiarly  brilliant1 soft and         
beautiful flame2 it requires no trimming
 or  snuffing to keep the flame of an   
equal brightness4 ,like the light of the
  ,sun itself1 it only makes itself     
known by the benefit and pleasure it    
affords4    ,the gas flame is entirely  
free from smell4 ,the gas itself has a  
disagreeable odour before it is burnt1  
and so has the vapour of wax1  tallow   
and oil1 as it comes from a candle or   
lamp newly blown out4 ,this  concession 
proves nothing against the flame of gas1
 which is perfectly  inodorous4    ,the 
gas-light flame is perfectly steady2 a  
benefit which persons  accustomed to    
read or write by candle-light1 are      
particularly capable of  appreciating4  
,with the other modes of illumination we
 have never the  light of the same      
intensity for two minutes together1     
independent of  that unpleasant dancing 
unsteady flame which is so harassing to 

the  sight4    ,the size1 form and      
intensity of the gas flame1 are         
regulated by simply  turning the        
stop-cock which admits the gas to the   
burner or lamp4 ,the  flame may at      
command be made to burn with an         
intensity sufficient to  illuminate     
every corner of a room1 or so low and   
dim1 as barely to be  perceived4 ,it is 
unnecessary to point out how valuable   
lights of this  description are in      
nurseries1 stables1 warehouses1 and     
chambers of the  sick4 ,from the        
facility with which the gas flame can be
 conveyed in  almost any direction1 from
 the diversified size and shape which it
 can  be made to assume1 there is no    
kind of light so well adapted for       
ornamental illumination4    ,the flame  
of coal gas is of a pure white colour1  
and of a body full and  compact4 ,in    
large masses1 it becomes of the same    
flickering character  which is common to
 all flames of large dimensions1 and is 
owing to the  agitation of the          

surrounding heated atmosphere4    ,the  
saving of labour connected with the     
employment of gas-light1 may  seem on a 
small scale to be trifling2 but when it 
is considered that in  large            
manufactories1 it is not unusual to find
 several persons employed  for no other 
purpose than trimming the lamps or      
setting and snuffing the  candles of the
 establishment1 the advantage gained on 
this head by the  use of a species of   
light which require no sort of attention
 whatever1  cannot but appear very      
considerable4    ,the cleanliness of the
 gas-lights is also a consideration of  
no small  importance1 they are attended 
with none of that spilling of oil1 and  
dropping of grease1 which makes the     
employment of oil-lamps and candles  so 
injurious in many warehouses1 shops and 
private dwellings4    ,the flame of a   
gas-light compared in point of          
brilliancy to that of a  candle1 is as  
the flame of a common oil lamp1 compared
 to the flame of a  lamp of ,argand4    

,the difference between a street1 on the
 night of a  general illumination1 and  
any other night when the street is under
 the  dull glimmering light of the      
ordinary oil lamps1 is scarcely more    
remarkable1 than the difference between 
a street lighted by gas1 and one        
lighted by oil4 ,while the ordinary oil 
lamps may be said merely to serve  the  
purpose of making 8darkness visible10   
the gas-lights really dispel  the       
dominion of night1 and diffuse a body of
 light so wide-spreading and  intense1  
as almost to rival the clearest         
moonshine4    ,the same brilliancy which
 makes the gas-lights of such utility   
out of  doors1 in lighting the streets1 
has been found of equal advantage in    
illuminating the interior of private    
dwellings1 and large public  buildings1 
such as churches1 and theatres1 c4 ,from
 a cluster of  gas-lights1 fewer by     
one-half than the number of oil lamps   
and candles  required for lighting up a 
public edifice of this description in   

the  most ordinary manner1 a body of    
light is furnished which diffuses       
through the whole1 a degree of mellow   
clearness which is not to be  attained  
by the greatest number of oil lamps1 or 
candles1 which a due  regard to         
respiration will admit of being         
employed4 ,as examples of this1  we have
 only to name the public theatres of the
 metropolis1 all of which  are lighted  
with gas1 and in a manner which excites 
universal  admiration4    ,it may       
perhaps be imagined that with a         
substance so inflammable1 and  amidst   
the blaze of resplendent flame which    
produces such beautiful  effects1 there 
is a peculiar risk of accidents by fire1
 but so far is  this from being the     
case1 that gas-lights are the safest of 
all lights4  ,no danger can arise from  
these lights in any way1 but what is    
common to  candle lights and lamps of   
all kinds1 and is the fault of none of  
them4  ,the gas-lights are in fact a    
great deal less hazardous4 ,there is no 

risk  of those accidents which often    
happen from the guttering of candles1   
from sparks being detached1 or from     
carelessly snuffing them4 ,the          
gas-light lamps and burners1 must       
necessarily be fixed to one place1 and  
therefore cannot fall or otherwise      
become deranged1 without being          
immediately extinguished4 ,and further1 
at any time by shutting the main  tube  
which conveys the gas to the burners and
 lamps1 all the lights in  the house can
 be immediately extinguished4 ,in short1
 where gas is used1  the master of the  
house1 when he has turned the main      
stop-cock which  conveys the gas into   
the collateral branch pipes1 may retire 
to rest  free from any of those         
apprehensions1 which before harassed    
him1 lest a  candle might have been left
 burning1 of lest the accidental        
dropping of  a spark might become the   
cause of enveloping himself and family  
in  destruction4    ,but the best proof 
of the great safety of the new lights   

is1 that  notwithstanding upwards of    
fifty-one thousand gas-lamps burn       
nightly in  ,london1 we have not heard  
of a single accident occasioned by them1
  though the lamps and burners are      
generally carelessly managed1 while we  
have too often occasion to lament the   
effects arising from sparks of  candles1
 or carelessness in snuffing them4      
,hence the fire-insurance-offices engage
 to insure manufactories and  public    
works1 at a less premium1 where gas is  
used1 than when lighted by  other means4
    ,the excessive expence of insurance1
 arising from the numerous candles      
employed in most of the first-rate      
manufacturing establishments1 and the   
combustible nature of the structure of  
the buildings2 the great  difficulty of 
retrieving the injury resulting to a    
well-organised  business1 from the      
accidental destruction of the machinery1
 are  considerations alone sufficient to
 furnish the strongest economical1 as   
well as political recommendations1 for  

the adoption of the new lights in  all  
manufactories where work is done by     
candle-light4    ,we have as yet only   
adverted to the application of gas in   
the more  ordinary cases where light is 
wanted1 but among other special purposes
  to which gas-lights may be applied1 it
 would be improper to overlook the      
peculiarly advantageous use which may be
 made of them in the supplying  of      
light-houses4 ,from the splendour and   
distinguishing forms which the          
gas-light flame is capable of assuming1 
nothing can possibly be better          
calculated for such a purpose2 and in   
point of economy1 the employment  of it 
would be attended with a saving of at   
least one half of the  ordinary expence 
of oil lights4 ,by means of a single    
furnace1 as much  gas may be produced in
 three hours1 as will furnish during the
 longest  winter night1 a flame of      
greater brilliancy than is now furnished
 by any  lighthouse in ,britain1 or     
indeed in the world4 ,the body of flame 

may be  increased to any size1 merely by
 increasing the number of burners2 and  
whatever may be the magnitude of the    
flame1 it will continue to burn1        
without becoming in the least clouded by
 smoke1 or the reflectors being  in the 
least obscured4 ,should these           
considerations lead1 as it is to be     
hoped they will1 to the actual          
employment of gas in the lighthouses    
around the ,british islands1 it will    
readily occur1 that in proportion as    
the gas would be found attended with    
less expense than the present mode  of  
lighting by oil1 it would enable the    
commissioners for light-houses1  out of 
the surplus means which would be thus   
placed at their disposal1  to multiply  
the number of lighthouses1 and thus to  
add most essentially  to the security of
 ,british navigation4 ,nor is it in the 
case of maritime  signal-lights alone1  
that the use of gas is applicable1 by   
its superior  efficacy and cheapness4   
,the saving of expences to the country  

which  would be effected by the         
substitution of coal gas1 for oil and   
tallow in  these and other public       
establishments1 is a consideration which
 cannot  be too much pressed on public  
attention4 ,the annual expenditure for  
lighting the barracks of ,great ,britain
 alone1 is said to fall little  short of
 fifty thousand pounds2 for less than   
one half of which sum1  they might be   
lighted by means of gas much better1 and
 a great deal more  safely4 ,some idea  
may be formed from the practical saving 
in this  department--how great might be 
the total saving1 were this new mode of 
lighting adopted in all our national    
establishments4    ,in the case of the  
public arsenals1 however1 the saving    
from the  employment of coal gas is a   
consideration of far inferior importance
 to  the superior security attending it4
 ,on the preservation of the stores     
which they contain may depend in a time 
of war the whole chance of  success     
against the enemy nor can any body who  

has lived in this  country at such a    
time have forgot the feverish alarm with
 which the  people have frequently seen 
this security endangered by accidents   
arising from the use of moveable lights4
 ,were coal gas exclusively  employed in
 such establishments1 the fixed position
 which can be given  to the burners1 and
 the absence of all danger from sparks  
must give a  degree of security to those
 places from fire1 far beyond what they 
at  present possess1 even when          
superintended with the greatest possible
  caution and fidelity4    ,the same    
remark is equally applicable to the     
government offices1 public  libraries1  
museums1 in short1 to all public        
establishments where the  national value
 of the articles preserved is such that 
no possible  means of increasing their  
security from destruction should be     
neglected4    ,we have now to turn our  
attention to another general point of   
view in  which the introduction of      
lighting by gas is not less an object of

  interest to the public2 we allude to  
the application of gas as a means  of   
heating as well as lighting4 ,mr4       
,maiben#a was the first who  directed   
the attention of the public to this     
subject2 he ascertained  that gas from  
coal gives nearly the same heat when put
 into combustion1  which is yielded by a
 third part of the coal from which it is
 extracted4  ,in other words1 it has    
been found that a quantity of fuel      
giving a  particular degree of heat1 may
 be employed so as to produce at the    
same  time another substance yielding   
nearly an equal degree of heat in a     
different and more manageable form2 a   
form in which it can be preserved  for  
any length of time1 divided into any    
portions1 distributed in any  direction1
 consumed in an open fire-place1 or in a
 stove concealed in  any shape2 a form  
in which the flame may issue equally    
well from iron or  from stone-ware1 be  
instantly lighted up and instantly      
extinguished1 be  made to burn as long  

or as short a time as may suit us1 and  
in any  degree of intensity between the 
most animating and brilliant blaze and  
its total extinction2 be extinguished in
 one room1 and the next moment  lighted 
up in any other2 in short such a form1  
that by one proper  arrangement from the
 beginning1 with the same portion of    
fuel1 we may at  any time have the      
command of a chearful fire1 an adequate 
and  comfortable warmth in any part of  
our dwelling to which we may have       
occasion to move1 as manageable1 and in 
this way as portable1 as the  taper by  
the touch of which it is kindled4 ,to   
those who have been  accustomed to see  
before them a solid mass of burning     
fuel1 this gas  flame may at first have 
the less satisfactory appearance of a   
fugitive  blaze which we perceive       
nothing to support4 ,but its uniformity 
and  permanence will soon banish this   
impression1 while it is attended with   
other advantages not inconsiderable with
 respect either to comfort or           

convenience4 ,there are no coals to be  
carried in1 no ashes to be carried  out2
 there is no blowing1 no sweeping of    
cinders1 no dust1 no  interruption of   
servants2 there is no excessive heat in 
one stage1 no  sudden damping at        
another3 we have the choice of any      
temperature1 and  which we can regulate 
with the utmost ease4 ,the fire itself  
is lively  and pleasant to the eye3     
inclosed in transparencies it receives a
 degree  of splendour not easily        
imagined4 ,numerous applications of gas1
 as a  source of heat for airing rooms1 
and other purposes1 have already been   
adopted4 ,it is used in kitchens for    
keeping meat warm1 and for boiling      
water2 in store rooms1 in picture       
galleries1 in libraries1 for            
maintaining them at an equal            
temperature4 ,by copper-plate printers1 
it  is used for warming their plates2   
and by jewellers and other artists1  for
 soldering4      #a ,a ,statement of the
 advantages to be derived from coal     

gas4--p4    #db4    ,it remains further 
to be observed that the coal1 by        
yielding gas and  other products1       
namely1 tar1 pitch1 and ammoniacal      
liquor1 is not  entirely lost4 ,it      
produces1 besides light1 an excellent   
fuel1 namely1  coke2 and as a           
manufactory1 or workshop1 generally     
requires heating as  well as lighting1  
there is a gain both ways4 ,the         
manufacturer1 by  distilling his coal   
instead of burning it as it comes from  
the pit1  saves his candles and improves
 his fuel4 ,one effort at the outset in 
erecting a gas apparatus1 will reduce   
his annual disbursement for those  two  
articles of prime necessity1 much in the
 same manner1 though in a  greater      
degree1 as the farmer gains by building 
a thrashing machine and  laying aside   
the use of the flail4    ,the coal is so
 far from being reduced in consequence  
of the gas-light  process1 to an useless
 mass1 that in many places immense      
quantities are  reduced to the state of 

coke for the purpose of rendering the   
coal a  better fuel than it was in its  
natural state2 for coke gives a strong  
and lasting heat4 ,it is equally        
valuable for kitchen and parlour fires1 
and still more as a necessary requisite 
in some important branches of           
manufacture1 so that in whatever        
quantity coke may be produced1 it can   
never want a good market4 ,the demand   
for coke in this capital1 since the     
establishment of the gas-light works1   
has prodigiously increased4  ,numerous  
taverns1 offices1 and public            
establishments1 which heretofore  burnt 
coal1 now use coke to the total         
exclusion of coal2 and in almost  every 
manufactory1 which requires both        
extensive lighting and heating1  gas and
 coke are now the means jointly         
employed4 ,a coke fire emits a  very    
uniform and intense heat2 it produces no
 sparks1 and burns free  from soot and  
smoke2 it requires no trouble in        
managing1 and to those  who have the    

misfortune of being plagued with a      
smoaky chimney1 affords  the only       
certain cure4    ,another valuable      
product is the tar which is deposited   
during the  production of the gas1 this 
tar when rectified by a slight          
evaporation1  has become an article of  
commerce4 ,large establishments1 both of
 coal  tar1 coal oil1 and pitch1 are in 
full action1 and the commodities which  
they furnish have become in great       
demand4 ,the ammoniacal liquor which    
the gas-light process affords1 has of   
late given rise to very important       
branches of chemical manufacture1       
carried on upon a large scale4 ,but as  
the gas is at present supposed to be the
 only object in view1 for the  sake of  
the light which it yields1 the other    
products being only  accidentally       
connected with its extraction1 let us   
leave the idea of  profit on them out of
 the question1 and with the utmost      
latitude of  concession1 require them   
only to stand as in part for a portion  

of the  coal employed in the process1 we
 have still the gas1 an article which   
performs the functions of the oil1 the  
tallow1 or the wax for which it  is     
substituted2 and to the price of which  
we have no need to call the  attention  
of those who make use of them4 ,there   
remains only to be  opposed on the other
 side1 the expence of the apparatus by  
which the gas  is to be prepared1 and   
the lights maintained4 ,from the        
materials and the  workmanship1 with the
 interest of the capital sunk1 the      
expence in the  first instance1 must be 
very considerable4 ,but where the       
quantity of  light must be great1 even  
from cheap substances1 or where1 with a 
less  quantity of light1 the substances 
from which it is derived must be of  the
 costliest kind2 such is in either case 
the enormous expence of these           
materials1 that by superseding them and 
making every reasonable  allowance to   
the engineer who erects the gas         
apparatus1 the sum it  costs1 both      

principal and interest1 is soon         
liquidated1 leaving at last  a total    
saving1 excepting the expence of        
accidental repairs1 which1 from  the    
durability of the materials employed1   
seldom exceeds a trifling sum4    ,the  
principal expence in the pursuit of this
 new branch of civil and  domestic      
economy1 is therefore1 the dead capital 
employed in erecting  the machinery for 
obtaining and conveying the gas4 ,the   
floating capital1  after the first cost 
incurred in erecting the apparatus1 is  
comparatively small2 even if usurious   
interest is allowed for the first  cost 
of the apparatus1 and its deterioration1
 the saving must always be              
considerable1 especially if the number  
of lights furnished are  comparatively  
in a small place4    ,at the same time  
were we to offer advice to the public on
 this subject1  it would be1 that no    
private individual resident in ,london1 
should  attempt to light his premises1  
for the sake of economy1 with coal gas  

by  means of his own apparatus1 whose   
annual expence for light does not       
exceed forty pounds4 ,but when a street1
 or small neighbourhood is  required to 
be lighted the operation may be         
commenced with safety2 the  sum required
 for erecting the apparatus1 and the    
labour attending the  process1 together 
with the interest of money sunk1 will   
then soon be  liquidated by the light   
and other products4    ,individuals have
 accordingly engaged successfully in the
 distillation of  coal1 and trade with  
advantage in the articles produced by   
the process4    ,in like manner may the 
lighting of cities be accomplished      
without the  aid of incorporated bodies2
 and parishes may be lighted by almost  
as  many individuals as there are       
streets in a parish4    ,the supplying  
of light to the street or parish lamps  
alone1 of any  district of street lamps 
only1 can never be undertaken with      
economy in  this capital1 nor indeed in 
any other2 for the money sunk in        

furnishing  the mains or pipes only1    
must always greatly exceed what any     
revenue  from the lighting of the       
streets alone can compensate4    ,the   
most beneficial application of          
gas-lights unquestionably is in all     
those situations where a great quantity 
of light is wanted in a small  place2   
and where light is required to be most  
diffused1 the profit of  this mode of   
illumination is the least4 ,hence1 the  
lighting of the  parish1 or street-lamps
 alone1 without lighting shops or       
houses1 can  never be done with economy4
    ,it may be objected to the          
universality of our conclusion that the 
price  of coal differing very much in   
different places will occasion a        
variation in the expence of the new mode
 of lighting4    ,the price of coals can
 however have but little effect upon the
 cost of  the gas-lights2 because the   
very refuse1 or small coal1 which pass  
through the screen at the pit's mouth1  
and which cannot be brought into  the   

market1 nay1 even the sweepings of the  
pit1 which are thrown away1  may be     
employed for the production of coal-gas4
 ,it makes no difference  in what form  
the coal is used4 ,this circumstance may
 contribute to  enable coal-merchants to
 furnish coals in larger masses1 and as 
they  come from the mine1 instead of    
increasing the bulk by breaking them    
into  a smaller size1 which is a        
practice commonly followed4    ,the     
demand which the gas-light occasions for
 inferior sorts of coal may  hereafter  
contribute to lower the price of the    
superior kinds1 and keep  a level which 
cannot be shaken under any              
circumstances4 ,it may  contribute to   
prevent combinations which do certainly 
operate to the  prejudice of the public1
 and sometimes put this great town at   
the mercy  of a few proprietors in the  
north1 who deal out this commodity in   
any  way they please4 ,the competition  
thus produced1 it is impossible not to  
consider as an advantage1 which would   

tend to prevent such combinations1  and 
put the inhabitants of ,london out of   
the reach of them4    ,the advantages   
which the coal trade must reap from the 
introduction of  the gas-light must be  
very considerable4 ,there is already    
less waste1  but a greater consumption  
of coal than formerly4 ,the lower       
classes of  the community are scantily  
supplied with firing2 and nothing but a 
reduction of price is necessary to      
increase to a very large amount the     
average quantity of fuel consumed in the
 country4 ,the lightness of the  coke   
produced by the gas-light manufacture   
diminishing the expence of  land        
carriage1 facilitates its general       
diffusion--the comforts of the  poor are
 becoming materially augmented1 and a   
number of useful  operations in         
agriculture and the arts are beginning  
to be carried on1  which have been      
hitherto checked by the extravagant     
price of fuel4 ,if  any additional vent 
were wanted for the coke1 it would      

readily be found  in the continental    
market2 coke being better suited than   
coal to the  habits of most ,european   
nations4    ,many1 and unquestionable as
 are the advantages of this new mode of 
procuring and distributing light1 it was
 not to be expected that an  invention  
which went to impair a branch of trade1 
in which a large  portion of skill and  
capital had hitherto been successfully  
employed  should escape encountering    
very considerable opposition4 ,on the   
first  introduction of the gas-lights1  
great but happily unsuccessful          
endeavours were made to alarm the public
 mind by dismal forebodings of  the     
destruction which would ensue to the    
,greenland trade1 and the  consequent   
loss of a valuable nursery of ,british  
,seamen4 ,when  impartially considered  
it will be found that there was nothing 
more in  this objection than the common 
clamour that is always set up against   
every new means of abridging labour1 to 
which had the public listened1  an      

interdict would have been laid upon the 
spinning and threshing  machines1 the   
steam engine1 and a thousand other      
improvements in  machinery4    ,such    
clamour scarcely ever fails to be made  
when the extension of  machinery1 the   
application of inanimate power1 and the 
abridgment of  labour consequent on     
either1 is a matter proposed4 ,we are   
then sure to  be told that the scheme of
 mechanical or chemical improvement is  
pointed  against the human species1 that
 it tends to drive them out of the      
system  of beneficial employment and    
that1 on the whole1 the sum of the      
improvement is not only a less          
proportion of good to society1 but a    
positive accession of misery to the     
unemployed poor4    ,the misfortune of  
this argument is that to be good for any
 thing1 it  would prove a great deal too
 much4 ,it is not confined in its scope 
to  any particular species or defined   
extent of improvement1 but is equally   
proscriptive of all improvements        

whatever4 ,it is a principle for savage 
life1 not for a state of civilization4  
,it takes for its basis that it is  an  
advantage to perpetuate that necessity  
for hard and incessant labour  under    
which man finds himself originally      
placed by nature1 with all the  wants1  
privations1 ignorance and ferocity1     
which are attendant on that  condition1 
and that every discovery1 invention1 or 
improvement which  tends to abridge the 
quantity required of human labour1 and  
to augment  the resources for living and
 enjoyment is a serious injury to       
society4  ,the advocates of this narrow 
theory do not go the whole length of    
maintaining that diminishing labour1 and
 increase of substance1 are in          
themselves positive evils1 a position   
too absurd perhaps for any one to       
uphold2 but they maintain what ends in a
 consequence nearly as untrue1  namely1 
that neither the one nor the other is of
 any advantage to  society at large4    
,the palpable error of this theory is1  

that it supposes  that all improvements 
which tend to supersede human labour1   
are  necessarily made for the benefit of
 a few1 and not for the common  benefit 
of the many2 that instead of lessening  
to each individual the  share of labour 
requisite to obtain the means of his    
subsistence1 their  only tendency is to 
lessen the value of each personas       
labour1 and to  oblige him to work more 
in order to live equally well4    ,now1 
however the existing state of things may
 be in this country1 or in  other       
countries1 arising out of a variety of  
arbitrary circumstances1  foreign to the
 natural1 and in all cases the          
ultimately inevitable  course of        
industry1 it is a matter of justice1    
clear and undeniable1  that every       
improvement in society ought to be the  
property of the many1  and not of a few2
 and that it ought either to lessen the 
quantity of  labour necessary for       
acquiring the means of living1 or to    
increase the  profit to be gained by    

continuing the same quantity of labour4 
,nor does  there seem any reason for    
believing that1 in point of fact1 the   
actual  distribution of things is so far
 from according with this principle of  
justice as some superficial and         
prejudiced observers are fond of        
representing4 ,the labourer1 or artizan1
 may now work a greater number of  hours
 daily than he did years ago2 but how   
seldom do we find this to be  the case  
without his comforts being more than    
proportionally multiplied1  and his     
ultimate independence from labour       
essentially promoted4 ,in  general1     
however1 the fact is1 if we may give    
credit to well informed  economists1    
that the working classes do not labour  
more than formerly1  and yet live1 or at
 least have the means of living better2 
and that by  working even less than     
formerly1 they can obtain the means of  
living  quite as well4    ,let the real 
state of matters in this respect1       
however1 be as it may1  the question    

comes to be one merely as to the        
distribution of the  produce of nature  
and of art1 and instead of opposing     
improvements  because they tend to      
encrease that produce1 the object of    
those who have  really the good of their
 fellow-creatures at heart1 ought to be1
 to  encourage such improvements as much
 as possible1 but at the same time to   
obtain a correction of any partiality or
 injustice which may have crept  into   
the distribution of their beneficial    
consequences4 ,it is not to be  denied  
that all new improvements which         
interfere with and change the           
occupations and habits of the working   
classes of people1 must at first  expose
 them to inconvenience and distress1    
against which it is in  fairness the    
duty of society to protect them2 but let
 not that temporary  inconvenience and  
distress which can and ought to be      
provided against1  be held as an        
insuperable obstacle to the adoption of 
an improvement the  ultimate tendency of

 which it is to better the condition of 
mankind4    ,it is likewise true that   
the manufacturing classes often suffer  
great  want by the occasional suspension
 of employment1 and sometimes actual    
oppression1 by the demand for labour2   
but that involves a question more       
immediately connected with political    
economy than the present subject4    ,it
 is not the machinery that is in fault  
in such cases1 but those  speculators   
who occasion an inordinate excess of    
employment1 or those  statesmen who1    
with their folly1 derange the great     
machine of human  interests and         
intercourse4    ,every invention which  
tends to diminish the labour of men must
 be a  benefit to the species2 and it is
 wicked to argue against the use of any 
thing from its occasional abuse4    ,if 
the application of mechanical inventions
 thus tends to improve the  humanity of 
the public1 if it reduces the necessity 
of hard labour1 and  diminishes the     
danger of many occupations which we     

contend it does1 they  who contribute to
 this object deserve our respect and    
gratitude4    ,it may be true that we   
have now no such minds as those of      
,homer1 or  ,bacon1 or others of their  
stamp2 but we should reflect that the   
circumstances which produced such       
characters are gone by1 and great       
faculties have found other objects and  
other materials to work with4    ,the   
use of mechanical industry not only     
improves and augments the  comforts of  
domestic life1 but it also1 perhaps1    
does as much to soften  the feelings of 
mankind towards one another as the      
precepts of  philosophy4 ,it tends to   
engender a detestation of hard labour1  
and to  make the world consider not what
 the labourer may be able to do in      
tasking him1 but what he ought to do    
without detriment to himself4 ,it       
effects this by withdrawing1 to a great 
degree1 from observation1 the           
distressing spectacle of men and animals
 toiling beyond their strength4    ,it  

ought never to be forgotten1 that it is 
to manufactories carried on  by         
machinery1 and abridgment of labour1    
that this country is indebted  for her  
riches1 independence1 and prominent     
station among the nations of  the world4
    ,authentic estimates have shewn1    
that the use of machinery in ,great     
,britain1 is equivalent to an addition  
to the population of upwards of  one    
hundred millions of adult persons4      
,this immense accession of power1 has   
enabled this country to withstand       
assaults1 and to achieve objects of     
political ambition1 that appear  almost 
miraculous when compared with the       
geographical extent and  numerical      
population of the kingdom4    ,with     
respect to what has been advanced as to 
the probable injury that  would result  
from the general adoption of the        
gas-lights all over the  country1 to the
 ,greenland trade1 it may be observed   
that the traffic  might with more       
propriety be called a drain than a      

nursery of the naval  force4 ,the nature
 of the ,greenland service requires that
 the crew should  consist of able bodied
 sailors2 and being protected men1 not  
subject to  the impress law1 they are   
rendered useless for national defence4  
,the  nursery of ,british seamen is the 
coasting trade2 and as the gas-light    
illumination becomes extended it will   
increase that trade as much as it       
diminishes the ,greenland fishery4      
,even on the extreme supposition that it
 would annihilate the ,greenland        
fisheries altogether1 we should have no 
reason to regret the event4 ,the        
soundest principles of political economy
 must condemn the practice of  fitting  
out vessels to navigate the polar seas  
for oil1 if we can  extract a superior  
material for procuring light at a       
cheaper rate from  the produce of our   
own soil4 ,the consequence of lighting  
our dwellings  and manufactories with   
gas can in fact prove injurious only to 
our  continental friends1 one of whose  

staple commodities1 tallow1 we shall    
then have less occasion to purchase1    
although the new lights can never       
supersede entirely the use of candles   
and moveable lights4          ,,part    
,,ii4      ,outline of the new art of   
procuring light by means of coal gas1   
and  ,theory of the production of ,gas  
,lights4    ,all substances1 whether    
animal1 vegetable1 or mineral1          
consisting of  carbon1 hydrogen1 and    
oxigen1 when exposed to a red heat1     
produce  various inflammable elastic    
fluids1 capable of furnishing artificial
  light4    ,the gases thus obtained are
 called carburetted hydrogen2 they      
produce1  from their combustion1 water  
and carbonic acid4 ,the species of      
carburetted hydrogen1 procured from     
pit-coal1 has of late been called  coal 
gas4    ,we perceive the evolution of   
this elastic fluid1 during the          
combustion  of coal1 in a common fire4  
,the coal1 when heated to a certain     
degree1  swells and kindles1 and        

frequently emits remarkably bright      
streams of  flame4 ,and after a certain 
period these appearances cease1 and the 
coal  glows with a red light4    ,the   
flame produced from coal1 wood1 turf1   
oil1 wax1 tallow1 or other  bodies1     
which are composed of carbon1 hydrogen  
and oxigen1 proceeds from  the          
production of carburetted hydrogen gas1 
evolved from the combustible  body when 
in an ignited state4    ,it must have   
been noticed at the same time1 that in  
the common mode of  burning coal in a   
fire-place1 or stove1 nearly the whole  
of this  inflammable gaseous matter is  
lost4 ,we often see a flame suddenly    
burst  from the densest smoke1 and as   
suddenly disappear2 and if a light be   
applied to the little jets that issue   
from the bituminous part of the  coal1  
they will catch fire and burn with a    
bright flame4 ,the fact is1  that the   
greater part of the carburetted hydrogen
 gas1 capable of  affording light and   
heat1 continually escapes up the        

chimney1 during the  decomposition of   
the coal1 whilst only a small part is   
occasionally  ignited1 and exhibits the 
phenomena of the flame4    ,if coal     
instead of being burnt in the way now   
stated1 is submitted at a  temperature  
of ignition in close vessels1 all its   
immediate constituent  parts may be     
collected4 ,the bituminous part is      
melted out in the form of  coal tar1    
there is disengaged at the same time a  
large quantity of an  aqueous fluid1    
contaminated with a portion of oil1 and 
various  ammoniacal salts4 ,a large     
quantity of carburetted hydrogen1       
carbonic  oxide1 carbonic acid1 and     
sulphuretted hydrogen also makes their  
appearance1 and the fixed base of the   
coal1 alone remains behind in the       
distillatory apparatus1 in the form of a
 carbonaceous substance called  coke4   
,an analysis of the coal is thus        
effected by the process of  destructive 
distillation4 ,the products which the   
coal furnishes may be  separately       

collected in different vessels4 ,the    
carburetted hydrogen1 or  coal gas1 when
 freed from the foreign gases may be    
propelled in streams  out of small      
apertures1 which when lighted may serve 
as a flame of a  candle and then form   
what we now call ,,gas ,,lights4    ,it 
is in this manner that from pitcoal a   
production of our own soil1 we  procure 
a pure1 lasting and brilliant light1    
which in other cases must  be derived   
from materials in part imported from    
abroad4    ,in order to apply this mode 
of procuring light on a large scale as  
now  practised with unparalleled success
 in this country1 the coal is put  into 
vessels called retorts and furnished    
with pipes connected with  reservoirs to
 receive the distillatory products4 ,the
 retorts are fixed  into a furnace1 and 
heated to redness4 ,the heat developes  
from the coal  the gaseous and liquid   
products1 the latter are deposited into 
receivers1 and the former are conducted 
through water in which quick  lime is   

diffused by which the carburetted       
hydrogen gas is purified4 ,the          
sulphuretted hydrogen and carbonic acid 
which were mixed with it1 become        
absorbed by the quick-lime1 and the pure
 carburetted hydrogen is stored  up in a
 vessel called the gas-holder1 and is   
then ready for use4    ,from the        
reservoir in which the gas has been     
collected1 proceed pipes1  which branch 
out into smaller ramifications until    
they terminate at the  place where the  
lights are wanted and the extremities of
 the branch  pipes are furnished with   
stop-cocks to regulate the flow of the  
gas into  the burners or lamps4    ,the 
production of gas-lights1 is therefore  
analogous to that of flame  produced    
from tallow1 wax1 or oil4 ,all these    
substances possess1 in  common with     
coal1 the elements of certain peculiar  
matters1 which are  capable of being    
converted into inflammable elastic      
fluids by the  application of heat4     
,the capillary tubes1 formed by the wick

 of a candle1 or lamp1 serve the  office
 of the retorts1 placed in the heated   
furnace in the gas-light  process and in
 which the inflammable gaseous fluid is 
developed4 ,the wax  tallow or oil1 is  
drawn up into these ignited tubes1 and  
is decomposed  into carburetted hydrogen
 gas1 and from the combustion of this   
substance  the illumination proceeds4   
,in the lamp as well as in the candle1  
the  oil1 or tallow1 must therefore be  
decomposed before they can produce a    
light1 but for this purpose the         
decomposition of a minute quantity of   
the materials successively1 is          
sufficient to give a good light4 ,thus  
originates the flame of a candle or     
lamp4    ,nothing more therefore is     
aimed at in the gas-light process1 than 
to  separate the immediate products     
which coal affords1 when submitted to a 
temperature of ignition in a close      
vessel2 to collect these products in    
separate reservoirs1 and to convey one  
of the products1 the inflammable  gas1  

by means of pipes and branching tubes1  
to any required distance1 in  order to  
exhibit it there at the orifice of the  
conducting tube1 so that  it may be used
 as a candle or lamp4    ,the whole     
difference between the gigantic process 
of the gas light  operation1 and the    
miniature operation of a candle or lamp1
 consists in  having the distillatory   
apparatus at the gas-light manufactory1 
instead  of being in the wick of a      
candle or lamp4 ,in having the crude    
inflammable matter decomposed previous  
to the elastic fluid being  wanted1 and 
stored up for use1 instead of being     
prepared and consumed as  fast as it    
proceeds from the decomposed oil1 wax or
 tallow2 and lastly1  in transmitting   
the gas to any required distance1 and   
igniting it at  the burner or lamp of   
the conducting tube1 instead of burning 
it at the  apex of the wick4 ,the       
principle of the gas-light manufacture  
is  therefore rational1 and justifiable 
by the general mode in which all  light 

is produced4    ,it only remains to be  
observed that while the new and         
important use to  which pitcoal may thus
 be applied1 affords a strong           
confirmation of what  has been well     
observed1 that of all subterraneous     
combustible  substances1 coal is in this
 country by far the most important      
natural  production4#b 8,it is connected
 not only with the necessities1 comforts
  and enjoyments of life1 but also with 
the extension of our most  important    
arts1 our manufactures1 commerce and    
national riches4      #b ,davy on the   
,safety ,lamp4    8,essential in        
affording warmth and preparing food1 it 
yields a sort of  artificial sunshine   
and in some measure compensates for the 
disadvantages of our climate4    8,by   
means of it metallurgical processes are 
carried on1 and the most  important     
materials of civilized life furnished1  
the agriculturist is  supplied with a   
useful manure and the architect with a  
necessary  cement4 ,not only            

manufactories and private houses1 but   
even whole  streets and towns are       
lighted by its application1 and in      
furnishing the  elements of activity in 
the steam-engine1 it has given a        
wonderful  impulse to mechanical and    
chemical ingenuity1 diminished to a     
great  extent human labour1 and         
increased in a high degree the strength 
and  wealth of the country40            
,,part ,,iii4      ,classification of   
,pit-coal1 and maximum quantity of gas1 
obtainable  from different kinds of     
,coal4    ,we have stated already that  
pitcoal is in this country the cheapest 
crude natural production from which     
carburetted hydrogen gas can be         
obtained in the large way4 ,it is that  
which yields it in abundance1 and  which
 can with the least trouble and expence 
be subjected to the  operation it has to
 undergo for the production of the      
gas4#c ,nature has  dealt this mineral  
out to us1 with an unsparing hand1 and  
has provided  mines of coal which seem  

to defy the power of man to exhaust4    
#c ,other ,substances from which        
carburetted hydrogen gas1 may be        
economically obtained1 are animal and   
vegetable oil1 tar1 both    vegetable   
and coal tar2 pitch1 resin1 the         
essential oils obtainable    from       
vegetable and from coal tar1 and the    
compact species of turf4 ,on    this    
subject we shall speak hereafter4       
,the principal coal mines in ,england   
are those near ,newcastle and           
,whitehaven4 ,the town of ,newcastle    
stands on beds of coal which extend to  
a considerable distance round the place1
 and which as far as concerns  many     
hundred generations after us1 may be    
pronounced inexhaustible4    ,pitcoal   
like all other bituminous substances is 
composed of a fixed  carbonaceous base  
in the state of bitumen1 united to a    
small portion of  earthy and saline     
matter1 which constitute the ashes left 
behind when  the coal is burnt4 ,the    
proportions of these parts differ       

considerably in  different kinds of     
coal2 and according to the prevalence of
 one or other  of them1 so the coal is  
more or less combustible1 passing by    
various  shades from the most           
inflammable coal into blind coal1       
,kilkenny coal1 or  stone coal1 and     
lastly into a variety of earthy1 or     
stony substances1  which although they  
are inflammable do not merit the        
appellation of  coal4    ,all the       
varieties of coal used in this country  
for fuel may be divided  into the       
following classes4    ,the first class  
comprehends those varieties which are   
chiefly composed  of bitumen only1 which
 take fire easily1 and burn briskly with
 a strong  and yellowish white blaze1   
which do not swell or cake on the fire1 
and  require no stirring1 which produce 
no slag1 and by a single combustion  are
 reduced to light white ashes4 ,some of 
this species of coal when  suddenly     
heated crackle and split into pieces1   
especially if laid on the  fire in the  

direction of the cross fracture of their
 lamin4    ,cannel coal1 deserves to be 
placed at the head of this class2 next  
to  this1 we may rank all those         
descriptions of coal known in the       
,london  market by the names of         
,hartley1 ,cowper's ,main1 ,tanfield    
,moor1 ,eighton  ,main1 ,blythe1 and    
,pont ,tops4 ,it also includes the sort 
of coals found in  several parts of     
,scotland1 called ,splent coal1 and some
 of those raised  on the ,western ,coast
 of ,england4    ,most of the coals     
raised in ,staffordshire ought likewise 
to be classed  among this species of    
coal1 but the line of distinction       
between these1  and the classes         
subsequently named1 cannot be accurately
 drawn4    ,the following table exhibits
 the maximum quantity of gas obtainable 
from  the first class of coal4#d      #d
 ,own ,experiments1 made at the ,royal  
,mint ,gas-,works4      ,one ,chaldron  
of ,coal1 produces             ,cubic   
feet of ,gas4      ,scotch ,cannel coal 

#ai1hij    ,lancashire ,wiggan coal     
#ai1fjh    ,yorkshire ,cannel coal1     
7,wakefield7                            
#ah1hfj    ,staffordshire coal1#e       
,first variety1#f                       
#i1gdh      ,second variety1            
#aj1bbc      ,third variety1            
#aj1hff      ,fourth variety1           
#i1gif    ,gloucestershire coal1#g      
,first variety1 7,forest of ,dean1 ,high
 ,delph7   #af1ehd      ,second variety1
 7,low ,delph7                   #ab1heb
      ,third variety1 7,middle ,delph7  
#ab1jif    ,newcastle coal1      ,first 
variety1 7,hartley7                     
#af1abj      ,second variety1 7,cowper's
 ,high ,main7          #ae1hgf          
,third variety1 7,tanfield ,moor7       
#af1ibj      ,fourth variety1 7,pontops7
                     #ae1aab      #e    
,they require a much higher temperature1
 than is necessary for the              
decomposition of ,newcastle coal4       
#f ,for the maximum quantity of gas     
produced from this and the three        

succeeding varieties of coal1 ,i am     
indebted to ,j4 ,gostling1 ,esq4        
,proprietor of the ,birmingham ,gas     
,works4      #g ,most varieties afford a
 porous1 and very friable coke4    ,the 
second class of coal1 comprehends all   
those varieties which contain  a less   
quantity of bitumen1 and a larger       
quantity of carbon than the  first      
class4 ,they burn with a flame less     
bright and of a more yellowish  colour1 
and the last portion of flame they are  
capable of yielding is  always of a     
lambent blue colour1 they become soft   
after having laid on  the fire for some 
time1 swell in bubbles and pass into a  
state of  semi-fusion1 they then cohere 
and coke1 puff up and throw out         
tubercular  scori1 with a hissing noise1
 accompanied with small jets of flame4  
,in consequence of the agglutination and
 tumefaction1 the passage of air1  if   
this sort of coal be burnt in an open   
grate1 is interrupted1 the fire  burns  
as it is called hollow1 and would become

 extinguished if the top  of the coal   
were not from time to time broken into  
with the poker4    ,the coke formed from
 this species of coal is more compact   
than that  produced from the first sort 
of coal1 and is well calculated for     
standing the blast of bellows in        
metallurgical operations4 ,in respect to
  weight the second class of coal is    
considerably heavier than those of  the 
first class1 the difference amounts to  
not less than from  twenty-eight pounds 
to thirty-three pounds in the sack of   
coal4 ,a  chaldron of some varieties of 
this class of coal1 if the coals are in 
large lumps1 weighs upwards of          
twenty-eight hundred weight4    ,the    
usual denomination by which the second  
class of coal is known in the  ,london  
market1 is that of strong burning coal4 
,the following varieties  are           
sufficiently known1 ,russel's           
,walls-,end2 ,bewick's and ,craister's  
,walls-,end2 ,brown ,walls-,end1        
,wellington ,main1 ,temple ,main1       

,heaton ,main1  ,killingsworth ,main1   
,percy ,main1 ,benton ,main1 and some   
varieties of the  ,swansea coal4    ,the
 smaller kinds of coal of this class are
 preferred by smiths1 because  they     
stand the blast well4 ,they make a      
caking fire so as to form a kind  of    
hollow1 space or oven1 as the workmen   
call it4 ,some varieties abound  in     
pyrites1 and others are intersected with
 thin layers of slate and  lime-stone4  
,they require more heat for being       
carbonized than the first  class1 and   
the fluid obtained from it by           
distillation1 contains a  considerable  
portion of carbonate1 sulphate1 and     
hydrosulphuret of  ammonia4 ,they are   
well calculated for the production of   
coal gas2 the  coke which they produce  
is not very brittle1 and will bear      
moving from  place to place1 without    
crumbling into dust4    ,the following  
table exhibits the maximum quantity of  
gas obtainable from  the second class of
 coal4#h      #h ,own ,experiments1 made

 at the ,royal ,mint ,gas-,works4       
,one ,chaldron of ,coal1 produces       
,cubic feet of ,gas4      ,newcastle    
coal1      ,first variety1 7,russel's   
,wall's ,end7                 #af1hgf   
,second variety1 7,bewick and           
,craister's ,wall's ,end7   #af1hig     
,third variety1 7,heaton ,main7         
#ae1hgf      ,fourth variety1           
7,killingsworth ,main7                  
#ae1cab      ,fifth variety1 7,benton   
,main7                         #ad1hab  
,sixth variety1 7,brown's ,wall's ,end7 
#ac1fjj      ,seventh variety1 7,mannor 
,main7                       #ab1edh    
,eighth variety1 7,bleyth7              
#ab1jif      ,ninth variety1 7,burdon   
,main7                         #ac1fjh  
,tenth variety1 7,wears ,wall's ,end7   
#ad1aab      ,eleventh variety1 7,eden  
,main7                         #i1fjj   
,twelfth variety1 7,primrose ,main7     
#h1cdh    ,the third and last class of  
coals includes those which are destitute
 of  bitumen1 being chiefly composed of 

carbon in a peculiar state of           
aggregation1 evidently combined         
chemically with much earthy matter4     
,coals of this class require a still    
higher temperature to become ignited    
than any of the former classes1 they    
emit little or no smoke4 ,when laid  on 
a fire they burn away with a feeble     
lambent flame1 indeed some  varieties   
give no flame at all1 but burn merely   
with a red glow1  somewhat like         
charcoal1 and at length become consumed 
without caking4  ,they leave a small    
portion of heavy ashes4    ,when        
submitted to distillation they afford   
little or no tar2 of a  consistence     
almost resembling pitch1 and a gaseous  
fluid chiefly  composed of gaseous oxide
 carbon and hydrogen gas4 ,it is        
scarcely  necessary to add that they are
 altogether unfit to be employed for the
  manufacture of coal gas4 ,the         
,kilkenny1 ,welch1 and stone or hard    
coal  belong to this class4 ,they       
require a strong draught when burnt in  

an  open fire-grate1 and the large      
quantity of gaseous oxide of carbon     
which  they furnish during their        
combustion is extremely offensive4 ,this
 is  particularly the case with         
,kilkenny coal4 ,the ,welch stone or    
hard coal  is better adapted for        
culinary purposes1 and there is reason  
to believe  that this species of coal   
might be rendered useful in the smelting
 of  iron ore1 by a slight modification 
in the metallurgic process employed  for
 extracting the metal from its ore1 but 
to eradicate prejudice1 and  to alter   
established practices is a work which   
nothing but time can  effect4 ,this     
species of coal is sent all over the    
kingdom2 it is well  calculated for the 
operations of drying malt and hops1 and 
its small  coal or culm has been found a
 more economical fuel1 than ,newcastle  
and  ,sunderland coals1 for the burning 
of lime and bricks1 and for all other   
processes where no blazing fuel is      
required4    ,the following table       

exhibits the maximum quantity of gas    
obtainable from  this class of coals4   
,one ,chaldron of ,coal1 produces       
,cubic feet of ,gas4      ,welch coal4  
,first variety1 from      ,tramsaren1   
near ,kidwelly1#i                       
#b1aaf      ,second variety1 from the   
yard vein at the same place    #a1fef   
,third variety1 from ,blenew1 near      
,llandillo              #a1daf          
,fourth variety1 from ,rhos1 near ,ponty
 ,barren            #a1bgb      ,fifth  
variety1 from the ,vale of ,gwendrath   
#a1bib      ,sixth variety1 from ditto  
#a1dhf      #i ,the coal for these      
,experiments was supplied gratuitously1 
to the    ,gas ,works of the ,royal     
,mint1 by ,sir ,w4 ,paxton of ,middleton
 ,hall4    ,when we consider the before 
mentioned varieties of coal in an       
economical  point of view1 as fuel to be
 used in the gas-light process1 for     
heating  the retorts1 it appears from a 
series of experiments that have been    
made  under my direction1 that the      

second class of coal comprehending those
  varieties which contain a larger      
quantity of carbon than bitumen 7p4     
#de17 afford the most economical fuel1  
they act less on the grate bars1  and   
fire bricks of the furnace than those   
varieties which take fire  easily and   
burn briskly with a strong blaze4 ,a    
mixture of ,welch ,stone  coal1 and     
,newcastle coal forms an excellent      
economical fuel1 where an  intense      
glowing fire is required4               
,,part ,,iv4      ,form and dimensions  
of the ,retorts originally employed for 
manufacturing ,coal ,gas4    ,the proper
 mode of constructing the retorts in    
which the coal is  distilled1 and the   
art of applying them form an object of  
primary  importance in every gas-light  
establishment4 ,according as the        
manufacture is conducted in these       
respects with a due regard to physical  
principles1 depends the quantity of gas 
which can be obtained in any  given     
time1 from any given quantity of coal1  

the consumption of fuel  requisite for  
the production of that quantity of gas1 
the degree of  deterioration to which   
the distillatory vessel is subjected1   
the quality  in some measure1 of the gas
 itself2 and1 as the ultimate result of 
all  these circumstances1 the cheapness 
at which the gas light can be  furnished
 to the consumer4    ,the essential     
influence of these various particulars  
on the value of the  art of lighting    
with coal gas1 has led to much assiduous
 enquiry to  ascertain that sort of     
construction and mode of operation in   
respect to  each of them which may be   
most advantageous4 ,and in no branch of 
the new  art of procuring light1 has a  
greater variety of plans of improvement 
been submitted to the several directing 
boards of gas works1 or more  labour and
 expence been incurred in experiments   
conducted on a large  scale1 to         
ascertain the relative merits of these  
plans4 ,nor is there any  part of the   
gas-light process in which a greater    

number of material  alterations have    
been put in practice4    ,in the earlier
 periods of lighting with coal gas the  
retorts employed at  some of the        
gas-light establishments in the         
metropolis1 were hollow  cast-iron cones
 from six to seven feet in length4 ,the 
greatest diameter  of the cone which    
formed the mouth of the retort1 measured
 from twelve  to fifteen inches1 and its
 smallest diameter at the vertex from   
nine to  ten inches4    ,at other gas   
works the form of the retort was a      
parallelopiped from six  to seven feet  
long1 the horizontal1 and vertical sides
 were  respectively to each other1 as   
#bj to #ae inches4 ,the angles of these 
retorts were slightly rounded4 ,fig4    
#af1 plate ,v4 exhibits a vertical      
section of this retort4    ,again at    
other establishments semi-cylindrical   
retorts1 placed  horizontally upon their
 flat surfaces were employed2 fig4 #ah4 
pl4 ,v4 ,the  length of these retorts   
was from five to six feet1 and their    

vertical  and horizontal diameters were 
to each other as #f inches1 to #ah      
inches4  ,and at a few establishments1  
ellipsoidal retorts1 fig4 #ag1 plate ,v4
 were  used2 these measured from five   
feet and a half1 to six feet in length1 
their major and minor axes bore         
different proportions to each other at  
different establishments4 ,at the first 
adoption of these retorts1 the          
proportions varied but little from the  
cylinder1 but subsequently the          
difference between the major and minor  
axes became gradually increased  till at
 last the major axis has become to the  
minor axis1 as #bj to #aj  inches1 and  
at some gas works the proportions are as
 #be to #aj inches4    ,with vessels of 
these forms the distillatory process was
 carried on for  some years1 and the    
quantity of fuel employed to decompose a
 given  quantity of coal by means of    
them1 amounted to from thirty to        
thirty-six per cent4    ,when the       
dimensions of the retorts were          

increased1 both the quantity of  fuel   
and time required for the decomposition 
of a given quantity of coal  was in a   
far greater ratio2 and the operations of
 charging and  discharging the retorts1 
very troublesome4    ,retorts of smaller
 dimensions have likewise been tried1   
but the more  frequent charging and     
discharging1 which they require1        
occasioned such a  waste of time and    
labour1 and such intermissions1 in the  
temperature  necessary for the process  
of distillation1 7besides being attended
 with  other disadvantages which will be
 afterwards explained71 that they were  
speedily discontinued at the gas works  
where they had been adopted4    ,the use
 of conical retorts1 as well as of those
 of a semi-cylindrical  and             
parallelopipedal form1 has of late been 
discontinued in most  establishments4   
,the conical shape not only diminishes  
the capacity of  the vessel1 but also   
renders it incapable of being heated    
economically4    ,from two comparative  

series of operations made on a large    
scale1 and  continued for upwards of six
 months with conical and cylindrical    
retorts1 with a view to determine the   
comparative power of these  vessels1 it 
has been proved that the same quantity  
of gas which can be  obtained by means  
of forty conical retorts1 may be        
procured in the same  time and with the 
same quantity of coal and fuel1 by means
 of  thirty-four cylindrical retorts4#aj
      #aj ,these ,experiments were made 
at the commencement of the new art of   
lighting with gas1 at the ,westminster  
,chartered ,gas ,works1 by ,messrs4     
,grant and ,hargraves4    ,similar      
experiments have been undertaken1 to    
determine the comparative  action of    
semi-cylindrical and parallelopipedal   
retorts4#aa ,the latter1  when kept in  
action day and night1 do not long retain
 their shape2 their  sides collapse1    
their capacity becomes diminished1 their
 angular form  causes the heat to act   
upon them unequally1 in whatever manner 

it may be  applied1 in consequence of   
which they suffer more deterioration in 
some  parts than in others4 ,besides1   
they require a much larger proportion of
  fuel for decomposing a certain        
quantity of coal than the cylindrical   
retorts4      #aa ,at the ,birmingham   
,gas ,works4    ,semi-cylindrical       
retorts1 with the base of the retort    
bent inwards1 so  as to give the vessel 
a kidney-shaped form1 have likewise been
 tried4  ,but this shape is still less  
advantageous2 they could not be made to 
work uniform1 they required more heat1  
and their deterioration was more  rapid 
than cylindrical retorts4 ,they could   
not be kept fit for use when  worked day
 and night1 more than about five months4
 ,and with regard to  ellipsoidal       
retorts1 it must be confessed1 that the 
experiments that  have as yet been made 
upon a large scale to ascertain their   
powers1 are  not of a nature to enable  
us to decide on their merits4 ,no       
experiments  have been carried on with  

retorts of this description in the      
metropolis  for a sufficient length of  
time1 with that care and attention which
 the  subject demands1 to ascertain     
their comparative power4 ,from what     
however  has been done1 there is reason 
to believe that ellipsoidal retorts1    
might be found more advantageous1 than  
those of a cylindrical form now  in use4
 ,an ellipsoidal retort1 #bj inches by  
#aj in diameter1 and six feet  long1    
weighs #ad ,cwt4    ,the reader will    
thus observe1 that of all the forms of  
retorts which  have been hitherto fairly
 tried1 upon a large scale1 it has been 
satisfactorily ascertained1 7excepting  
only as to the ellipsoidal  retorts71   
that the cylinder is the best form for  
decomposing coal in  masses1 from five  
to eight or ten inches in thickness4    
,it is perhaps needless to state that in
 making experiments on the  comparative 
value of the best form of cast-iron     
retorts1 it is obvious  that the        
operations should be continued for some 

months uninterruptedly2  no conclusion  
can be drawn that may become practically
 useful in the  large way1 from         
processes carried on for a few weeks    
only4 ,it is  absolutely essential that 
the comparative trials be continued for 
months  together1 and that the          
inferences be taken from the total      
quantity of  coal used during that      
period1 compared with the total quantity
 of gas  obtained1 the deterioration of 
the retorts1 and the time and labour    
expended4    ,proceeding on erroneous   
data1 many have persuaded themselves of 
having  noticed that parallelopipedal   
and semi-cylindrical retorts last longer
  fit for use than those of a           
cylindrical shape1 an assertion of which
  subsequent trials1 conducted in the   
manner just stated1 has clearly  shown  
the fallacy4 ,enough has been done at   
the different gas works in  the capital 
to settle this point1 and there is now  
but one opinion  amongst those who are  
best qualified to judge of the subject4 

,every body  who has made the trial on a
 large scale1 is convinced as already   
stated1  that the best form of the      
retort for manufacturing coal gas where 
the  process is conducted on the plan of
 decomposing coal in masses or layers   
of from four to eight inches in         
thickness1 is a cylinder six and a half 
feet long1 and one foot in diameter1 and
 accordingly retorts of this  shape and 
dimensions are now used in all the best 
regulated gas  establishments in the    
metropolis4    ,a cylindrical retort of 
the description before named1 weighs    
about nine  and a half to ten hundred   
weight4 ,these and all other shaped     
retorts are  furnished with a moveable  
lid or cover having a conical edge to   
fit the  mouth-piece2 the cover is      
rendered air-tight1 not as formerly by  
grinding1 a mode which was costly1 but  
by the interposition of a thin  coat of 
loom1 between the lid and the mouth of  
the retort4    ,the mouth-piece forms a 
separate part of the retort4 ,it is     

bolted and  screwed to a flanch which   
terminates the mouth of the retort1 so  
that  when the retort is worn out1 the  
mouth-piece may be detached and applied 
to new retorts4    ,there are now in    
action #fbj cylindrical retorts1 at the 
two chartered  ,gas ,works#ab in the    
metropolis2 and the total number of     
retorts at all  the ,london gas         
establishments amounts to #ifj4      #ab
                                        
,westminster ,station   #bej ,retorts4  
,westminster ,gas ,works1   ,brick ,lane
 ditto      #aij ditto                  
,norton ,falgate ditto   #ej ditto      
,city of ,london ,gas ,works1 ,dorset   
,street1        #acj ditto              
---                                     
#fbj      ,application of heat4--,flue  
,plan originally adopted4    ,it must be
 obvious that the durability of the     
distillatory apparatus1  greatly depends
 on the manner in which the heat is     
applied1 to effect  the decomposition of
 the coal contained within the retort4  

,if the heat  be very intense the whole 
vessel is rapidly destroyed4 ,if it be  
too  languid1 the distillatory process  
is protracted1 and much fuel1 time1  and
 labour wasted to no purpose2 and the   
retort is speedily  deteriorated1 if the
 heat acts upon one part of it more than
 upon  another4    ,the different kind  
of retorts of which a description has   
been given in  the preceding pages1 were
 originally heated by means of flues    
passing  under and over them4 ,the      
retorts were placed horizontally and    
fixed in  brick-work4 ,one fire-place at
 the extremity of the mouth of the      
retort  where the coals are introduced1 
and whence the coke is withdrawn1 was   
allotted to every two retorts in the    
series4    ,at the commencement of the  
new art of procuring light the quantity 
of  fuel as before stated1 necessary to 
decompose a given quantity of coal1     
amounted to from thirty to thirty-six   
per cent of the coal decomposed2  that  
is to say1 it required from thirty to   

thirty-six parts of fuel to  decompose  
one hundred parts of coal4 ,this        
quantity has been much  lessened by a   
better mode of setting the retorts1 and 
it is now the  general opinion that the 
operation of decomposing coal1 by means 
of  cylindrical1 parallelopipedal1 or   
semi-cylindrical retorts1 must be       
considered as well conducted when one   
hundred parts of coal are  decomposed by
 twenty or twenty-five parts of fuel4   
,this appears to be  the minimum        
quantity of fuel1 that can be employed  
for the complete  decomposition of coal 
by means of these retorts1 and with the 
least  deterioration of the distillatory
 vessel4    ,the following statement    
will exhibit what has been done in this 
branch  of art4      ,report on a course
 of ,operations1 made with sets of #ff1 
of #cj1 of #aaf1  and of #fd retorts1   
worked on the ,flue ,plan4    ,in order 
to determine the relative value of the  
best method of setting  cast-iron       
retorts1 it was deemed necessary to     

ascertain whether three  retorts might  
not be heated1 instead of two1 as before
 stated1 by one  fire-place and         
branching flues4 ,to determine this the 
following  processes were carried into  
effect4      ,process ,i4    ,sixty-six 
cast-iron cylindrical retorts1 of the   
usual size1 namely1 six  and a half feet
 long1 7exclusive of the mouth-piece7   
and one foot in  diameter1 internal     
dimensions1 where set on the plan of    
three retorts to  one fire-place1 at the
 ,westminster gas-work station1 and a   
series of #cj  similar retorts were     
erected at another station belonging to 
the same  company1 at the ,east end of  
,london4    ,the experiments were       
pursued with every degree of justice in 
the detail1  the retorts were kept in   
action day and night for upwards of four
  months1 and the results noted down    
with exactness4 ,the final reports  from
 the two establishments were found to   
concur in showing that nothing  was to  
be gained by this method over that      

previously in use4    ,the time occupied
 for the distillatory process was not   
abridged4 ,the  consumption of fuel was 
greater--no larger quantity of gas was  
obtained  from the quantity of coal     
carbonized4 ,the produce with regard to 
coke  was in the usual ratio1 and the   
retorts were destroyed in about one     
third less time than when only two were 
heated by one fire-place4      ,process 
,,ii4    ,the apparently conclusive     
results of these experiments did not1   
however1  prevent another set of        
experiments from being made on the same 
principle1 extended even a degree       
farther4 ,the problem now proposed to   
be solved1 was1 whether four retorts    
might not be heated with economy1  in a 
manner which had been found already     
wasteful with respect to three1  that   
is1 whether four instead of two retorts 
might not be heated  economically by    
means of one fire-place4    ,on this    
plan one hundred and sixteen cylindrical
 retorts of the usual  dimensions were  

again erected at the ,westminster gas   
establishment1 and  sixty-four at       
another station belonging to the same   
chartered company4  ,these retorts were 
kept in action in the best possible     
manner night and  day1 and the results1 
as might have been anticipated1 only    
served to  confirm the facts already    
established by experiment with three    
retorts4    ,nothing was found to be    
gained2 and so far from their being any 
saving  in respect of fuel and wear and 
tear of the retorts1 the waste beyond   
that which takes place on the plan of   
two retorts to one fire-place1  was     
increased to nearly twenty-five per     
cent41 accompanied by a  corresponding  
acceleration of injury to the retorts4  
,it was still imagined1 however1 that   
the great waste of fuel and the         
ultimate unfavourable result of these   
proceedings1 which were repeated  with  
as little success at several other      
gas-works in the metropolis with        
parallelopipedal retorts1 and at other  

works with retorts of a                 
semi-cylindrical form1 set in a way     
different from that pursued at the      
,westminster station1 might probably    
have been owing to the unavoidable      
circumstance1 that the heat was not made
 to act upon all the retorts  employed  
uniformly in each series of four        
retorts1 but in a manner so  variable   
that one1 or even two of the series     
would become destroyed and  rendered    
useless1 while the others continued     
uninjured in a sound and  working state4
    ,the excessive waste of fuel was    
occasioned1 we are told1 by the number  
of injured retorts1 which became        
useless1 and were nevertheless required 
to be kept red hot to no purpose2 for it
 was actually found that when  one      
retort of a series of four became       
injured1 the same fire which had  heated
 the whole four1 still required to be   
kept up to maintain in  action the      
remaining three of the series1 and so on
 with respect to the  whole range1 till 

ultimately when there might remain only 
eighty retorts  actually in use1 as many
 fire-places were required to be in full
 action  as would have been sufficient  
to serve for one hundred retorts4       
,attempts accordingly were now made to  
get over this supposed cause of  the    
losing results1 already obtained from   
the plan of four retorts to  one        
fire-place1 by a new series of similar  
operations1 in which the  retorts were  
fixed in such a manner1 that those which
 happened to become  injured during the 
process1 might easily and immediately be
 withdrawn  without materially          
disturbing the rest1 and replaced by new
 ones4 ,the  waste of fuel was1 it is   
clear1 greatly lessened by the          
expedient2 yet  still upon the whole    
there was no such variation from the    
general  results obtained by the        
preceding experiments1 as to justify the
  adoption of this plan of increasing   
the number of retorts worked by one     
fire-place1 on any principle of sound   

economy4    ,the great obstacle1 as the 
reader will at once perceive1 to working
 more  than two retorts1 no matter      
whether cylindrical1 or of any of the   
other  forms before named1 with economy1
 by means of one fire-place1 evidently  
arose from the difficulty of conducting 
the heat by means of flues  around the  
series of retorts1 in such a manner that
 the heat shall act  with equal force on
 all the retorts4    ,it is almost      
needless to state1 that the construction
 of the  fire-places1 and the direction 
of the flues for applying the heat to   
the  retorts1 were varied by different  
workmen1 who prided themselves on  being
 able to aid the object in view1 but the
 result always showed even  that when   
the draft of the fire-place was well    
obtained1 the action of  the heat upon  
the series of retorts could not be      
distributed equally and  kept up        
uniformly1 except at a great expence of 
fuel and vast  deterioration of the     
distillatory vessels4 ,the retorts      

always became  injured more in some     
parts than in others4 ,the concentration
 and  rapidity of the draught of the    
fire1 beyond a certain velocity was     
always found highly injurious to the    
retort1 and this observation has  been  
since amply confirmed4    ,in a well    
constructed furnace1 the deterioration  
of all the retorts in  the series is    
uniform over the whole vessel2 no part  
of the retort is  burnt out1 as the     
workmen call it1 sooner than another    
part2 and  whenever the contrary        
happens1 we may pronounce the fire to be
 badly  applied4 ,when there is such    
misapplication of the heat1 the         
manufacturer  cannot depend upon the    
duration of the distillatory vessel2 he 
is always  in a state of uncertainty    
with regard to their wear and tear1 and 
it not  unfrequently has happened1 under
 such circumstances1 that a whole series
  of retorts have become suddenly       
deteriorated4      ,oven plan lately    
adopted4    ,the results before         

detailed1 with regard to the mode of    
setting  cylindrical retorts suggested  
the propriety of an entire change in the
  mode of applying the heat1 and this   
was at length fully carried into  effect
 by the adoption of ovens1 or air       
furnaces1 in which the retorts  are     
equally exposed to the action of heat on
 all sides4 ,mr4 ,rackhouse  has the    
merit of having first carried into      
effect this method1 since  generally    
known by the name of the oven plan4     
,the first experiments with these ovens 
were made on only one retort1  exposed  
in an oven to air intensely heated2 but 
they were afterwards  repeated on two1  
three1 four1 and five retorts1          
successively4 ,the  retorts suffered the
 action of heat thus applied1           
exceedingly well2  their deterioration  
was uniform1 and the quantity of fuel   
required to  work them1 was found always
 to be in a direct ratio to the number  
of  retorts employed4 ,these experiments
 were carried on for upwards of nine    

months1 and it was found1 that with five
 retorts in one oven1 so that  the      
heated air could act upon all of them   
equally1 without the flame  being       
directed forcibly upon them1 this plan  
had a decided advantage1 in  point of   
economy1 over every other method        
previously adopted4 ,each oven1         
containing five retorts1 is heated by   
means of three fire-places1 and         
although it is true that the number of  
retorts is less by one1 than what  could
 have been heated by three fire-places1 
on the original plan of two  retorts to 
one fire1 yet still this method has been
 found to be far more  productive4 ,the 
front wall of the oven may be readily   
taken down so that  a retort1 when      
damaged1 may be withdrawn1 and replaced 
without  materially disturbing the rest4
    ,the oven plan of applying heat has 
been found equally advantageous for     
parallelopipedal and semi-cylindrical   
retorts4#ac      #ac ,the only gas-light
 establishment of great extent in the   

metropolis1 at which parallelopipedal   
retorts are still in use1 is the        
,south ,london ,gas ,works4 ,but it is  
solely owing to the very peculiar       
care and economy with which all the     
details of this establishment are       
conducted1 under the immediate          
superintendence of a few active1        
skilful and scientific proprietors1 that
 they are able to compensate    for the 
loss1 which in all ordinary cases is    
inseparable from the    employment of   
vessels of that description4            
,description of the ,retort ,oven4      
,fig4 #a1 plate ,,iv41 represents a     
transverse section of one of the retort 
ovens now in action at the ,westminster 
,chartered ,gas-,light ,company's       
,works2 similar ovens are likewise in   
use at the ,city of ,london ,chartered  
,gas-,light ,works1 and in many other   
provincial gas establishments4    ,fig4 
#b1 plate ,,iv41 exhibits a longitudinal
 section1 and fig4 #a1 plate ,v4  shows 
the front elevation of the oven1 built  

about ten feet above the  ground1 upon  
piers or arches1 which saves brick-work 
and allows a stage  or platform to be   
erected in front of the fire-places of  
the ovens4 ,see  fig4 #b1 plate ,,iv4   
,between the back part of the ovens and 
the wall of the building in which  they 
are erected1 is left an empty space of a
 few inches to prevent the  heat of the 
oven being communicated to the wall1 as 
is seen at ,y in fig4  #b1 plate ,,iv4  
,the whole interior of the oven1 as well
 as the horizontal flue which  pass     
underneath the crown of it1 near the    
upper tier of retorts1 is  lined with   
fire bricks4 ,the uppermost part or     
crown of the arch is  constructed of    
large fire bricks of such a shape as    
will allow to  flatten the upper part of
 the arch as much as possible1 in order 
to  contract the space between the two  
upper retorts and the crown of the  arch
 of the oven4    ,r4 ,r4 fig4 #a1 and   
#b1 plate ,,iv4 and fig4 #a1 plate ,v4  
are cylindrical  retorts1 placed        

horizontally in the oven1 the lower     
series are either  supported by a large 
fire-brick1 placed edgeways underneath  
the retort1  or by means of a stout     
wrought-iron pillar1 as shown in the    
design4 ,the  two upper retorts are     
supported by wrought iron straps1 ,t1   
,t1 ,t1 fig4  #a1 and ,t1 fig4 #b1 plate
 ,,iv4 ,the straps pass through the     
brick-work of  the upper part of the    
oven1 as shown in the designs1 and they 
are  secured with screws and nuts to an 
iron bearing bar1 the extremities of    
which are supported by the outer walls  
of the oven4 ,each retort is  furnished 
at the extremity opposite to the        
mouth-piece1 with a short  projecting   
piece or tail let into the brick-work of
 the oven1 as seen in  the design1 fig4 
#b1 plate ,,iv4    ,m4 ,fig4 #b1 plate  
,,iv4 shows the mouth-piece of the      
retort with its cross  bar and          
hand-screw2 and fig4 #f1 plate ,v4 shows
 the mouth-piece drawn to  a larger     
scale4 ,e4 is the hand-screw1 with its  

cross or bearing bar ,d1  which passes  
through the projecting arms ,c4 ,c4 ,the
 lid of the  mouth-piece has a conical  
edge1 so that it fits close when pushed 
into  its place by means of the         
hand-screw ,e4 ,fig4 #g1 plate ,v4 is   
the lid  which closes the mouth-piece2  
the handscrew ,e1 fig4 #f1 presses the  
lid  close1 to render it air-tight1 a   
thin stratum of loom luting being first 
applied to the orifice of the           
mouth-piece4    ,f4 fig4 #b1 plate      
,,iv41 is the fire-place1 with the      
ash-pit ,e of the  oven4 ,the door of   
the ash-pit is provided with three slits
 covered  within by a register slide1 to
 regulate the admission of air as       
occasion  may require4    ,the fire     
passes freely and uniformly round all   
the retorts1 and the  whole cavity of   
the oven acquires an equable            
temperature1 which it  retains1 if the  
workman takes care to admit as little   
air as possible1  through the register  
door of the ash pit1 when the upper part

 of the  arch1 or crown of the oven has 
acquired a bright cherry red heat4      
,we have stated already that in front of
 the oven1 is a platform1 as            
represented in the sketch1 fig4 #b1     
plate ,,iv4 ,in the floor of this       
platform1 and directly underneath the   
mouth-piece of the retorts1 all of      
which project beyond the brick-work of  
the oven1 is an opening covered  with an
 iron trap door2 through this door the  
red hot coke1 discharged  from the      
retorts1 is suffered to fall below the  
stage or platform into a  cellar1 or    
other fire-proof place1 that it may not 
annoy the workmen4 ,o1  ,o1 fig4 #a1    
plate ,v4 denotes this opening through  
which the coke falls4    ,p1 fig4 #b1   
plate ,,iv41 and ,p4 ,p4 fig4 #a1 plate 
,v4 is a pipe proceeding                
perpendicularly from the upper part of  
the mouth-piece of each retort1  the    
other extremity of which descends into  
the horizontal hydraulic main  ,h1 which
 is shown in fig4 #b1 plate ,,iv4 and   

plate ,v41 supported upon iron  columns4
 ,this pipe serves to convey away the   
liquid and gaseous products  which      
become disengaged from the coal in the  
retort during the  distillatory process4
    ,the liquid substances1 namely the  
tar and ammoniacal fluid1 collect in    
the hydraulic main ,h1 plate ,,iv4 and  
,v41 which is furnished with a          
perpendicular diaphragm or partition    
plate to cause a certain quantity  of   
the liquid deposited in it to accumulate
 to a certain height1 and  thus to seal 
the perpendicular pipe ,p4 ,the liquid  
cannot flow out of the  horizontal pipe 
,h1 till it rises to the level of the   
diaphragm4 ,this  arrangement is        
distinctly shewn at ,h4 fig4 #b1 plate  
,,iv41 where the  diaphragm or partition
 plate is seen in the section of the    
hydraulic  main1 together with the      
extremity of the perpendicular pipe ,p41
  descending into the fluid contained in
 the hydraulic main4    ,k1 ,fig4 #a1   
plate ,v4 is the discharging pipe1      

connected with the upper  part of the   
horizontal main ,h3 it serves to convey 
away the gaseous and  liquid products   
from the hydraulic main ,h4 ,by means of
 this pipe the tar  and ammoniacal      
fluids are conveyed into any convenient 
reservoir1 called  the tar cistern1     
which is perfectly air-tight1 and from  
this vessel the  liquid may be drawn of 
by means of a pipe or stop-cock4 ,the   
extremity of  the pipe which            
communicates with the liquid1 is bent   
downwards1 so that  no air can enter the
 vessel3 this arrangement is shown at   
fig4 #c1 plate  ,,ii4    ,it is         
essential that the condensation of the  
vaporous fluids should be  fully        
completed before they reach the tar     
cistern4 ,to effect this1 there  is     
usually allowed a considerable distance 
to intervene between the  discharging   
pipe ,k1 fig4 #a1 plate ,v41 and the    
reservoir destined to  receive the      
condensible products2 or the pipe is    
made to pass through a  vessel          

containing water1 called the condenser1 
which acts in a similar  manner as the  
refrigeratory of a common still4 ,it is 
obvious that it is  immaterial how the  
condensation of the vaporous fluid is   
effected2 it is  essential1 however1    
that the condensation should be complete
 before the  liquid tar and ammoniacal  
fluid reach the reservoir destined to   
receive  these products4    ,the gaseous
 fluid which accompanies the condensible
 products1 are then  made to pass into  
the lime machine1 of which we shall     
speak hereafter1  in order to be        
deprived by means of quick-lime and     
water1 from the  portion of sulphuretted
 hydrogen and carbonic acid gas which   
was  combined with the gas4 ,and when   
this has been accomplished1 the purified
  gas is conveyed into the gas-holder1  
where it is stored up for use4 ,this    
part of the operation will be rendered  
more obvious hereafter4 ,in some        
establishments1 the hydraulic main is   
furnished with two discharging  pipes1  

the one carries away the condensible    
fluid1 into which the  perpendicular    
pipes ,p1 fig4 #b1 plate ,,iv4 dip1     
whilst the other serves to  convey away 
the gaseous fluids to a condensor1 in   
order to deposit the  vaporous portion  
of condensible liquid it may contain1   
and from thence  the gas passes into the
 purifying apparatus1 or lime machine4  
,x1 fig4 #b1  plate ,,iv41 is a small   
screw plug1 which1 when opened1 restores
 the  equilibrium of the air within and 
without the retort previous to the lid  
being taken off1 to prevent the loud    
report1 which otherwise happens  when   
the lid or cover of the retort is       
suddenly removed4 ,to avoid these       
explosive reports which had become a    
nuisance to the neighbourhood of  gas   
works1 the practice of gradually        
withdrawing the lid of the retort1  and 
at the same time presenting a lighted   
torch has been adopted at some  works1  
which fully remedies the evil4    ,the  
number of retort ovens at the           

,westminster ,chartered ,gas ,works'    
,stations1 amounts to four hundred and  
ninety4          ,,part ,v4             
,difference in the quantity of ,gas     
evolved during different periods of  the
 distillatory process1 and economical   
considerations resulting  therefrom in  
the manufacture of ,coal ,gas4    ,in   
conducting the decomposition of coal1   
the evolution of the gas is far  from   
being1 with regard to quantity1 uniform 
during different periods of  the        
distillatory process4 ,the formation of 
the gas is more rapid in the  beginning 
of the process1 and gradually slackens  
as the operation  proceeds4 ,the gas    
also differs in its chemical            
constitution1 at  different periods of  
the process2 although in the case of    
large  supplies1 this difference is of  
little consequence after the gas is     
purified in the usual manner4 ,the      
former consideration1 however1 has      
given rise to various modes of          
operating1 of which it will be proper to

  take some notice4    ,it must be      
obvious1 that in proportion as the mass 
of coal in the retort  becomes          
carbonized or converted into coke1 the  
exterior surface becomes  a gradually   
increasing obstacle to the action of the
 heat upon the  interior or central part
 of the coal remaining to be decomposed4
 ,the  heat required on that account    
must be more intense1 and kept up to no 
purpose1 and the extrication of gas     
becomes slower and slower1 as the       
operation proceeds4    ,the loss        
occasioned by this rapid diminution of  
the means employed1 is  serious in every
 point of view1 in regard as well to the
 quantity of  fuel used and time wasted1
 but it is unavoidable in the operation 
of  decomposing coal in masses or layers
 from #e to #aj inches in thickness1    
and must be a great drawback on the     
value of the gas-light discovery4       
,the loss of fuel1 it is obvious1 must  
be just in proportion to the  quantity  
of carbonised matter1 or coke1 which is 

kept hot to no purpose1  awaiting the   
decomposition of that portion of coal1  
which it is the  very means of          
protecting from becoming decomposed4    
,a striking exemplification of this     
statement will be seen in the  following
 table1 exhibiting the result of the    
progressive produce of  coal gas1       
obtainable1 in a given time1 by means of
 cylindrical and  parallelopipedal      
retorts4    ,experiment with one        
cylindrical ,retort1 containing two     
bushels of  coal4      ,hours of the    
,quantity of ,gas    distillatory       
process       produced4      ,first hour
               #aae cubic feet          
,second ditto              #ha ditto    
,third ditto               #gh ditto    
,fourth ditto              #gj ditto    
,fifth ditto               #ff ditto    
,sixth ditto               #ee ditto    
,seventh ditto             #di ditto    
,eighth ditto              #db ditto    
---                             #eee    
cubic feet4    ,the quantity of gas is  

at the rate of ten thousand cubic feet  
to the  chaldron 7#bg cwt47 of coal4    
,experiment#ad with eighteen cylindrical
 ,retorts1 containing one  chaldron of  
coal4      ,hours of the                
,quantity of gas    distillatory process
       produced4      ,first hour       
#bjjj cubic feet    ,second hour        
#adhh    ,third hour              #adjj 
,fourth hour             #acja    ,fifth
 hour              #abjh    ,sixth hour 
#ajjj    ,seventh hour             #hig 
,eighth hour              #fia          
----                            #iihe   
,this experiment was made with retorts  
set on the flue plan4    ,the coal      
employed was 7,bewick and ,craister's   
,wall's ,end71 ,newcastle  coal4        
#ad ,communicated by ,mr4 ,t4 ,s4       
,peckston1 of the ,westminster ,gas     
,works4    ,experiment with thirty-six  
parallelopipedal retorts1 each          
containing  two bushels of coal4#ae     
,hours of the            ,quantity of   
,gas    ,distillatory ,process          

produced4      ,in the first hour       
#d1jeh    ,second hour                  
#c1jbh    ,third hour                   
#b1hga    ,fourth hour                  
#b1ebf    ,fifth hour                   
#b1chj    ,sixth hour                   
#a1iga    ,seventh hour                 
#a1ged    ,eighth hour                  
#a1dej                                  
------                                  
#bj1jch      #ae ,own ,experiments4     
,the same heat as we have seen from the 
preceding table1 p4 #gi1 which is       
necessary during the first hour of the  
operation1 for the evolution of  one    
hundred and fifteen cubic feet of gas1  
is required in the eighth  hour for the 
production of no more than forty-two    
cubic feet1 being a  decrease in effect 
of nearly two-thirds4    ,when larger   
retorts are employed for decomposing    
coal in masses1 from  five to ten inches
 in thickness1 the loss of heat is in a 
much greater  ratio4    ,in the hope of 
remedying in some measure the evils thus

 distinctly  ascertained to arise from  
the undue thickness of the masses of    
coal  subjected to the distillatory     
process1 there have not been wanting    
manufacturers who have had recourse to  
experiments on a large scale1 to        
ascertain with certainty whether they   
might not be gainers by suffering  the  
distillatory process1 when the retorts  
are charged with two bushels  of coal1  
to proceed only for the space of six    
hours1 instead of eight4  ,but the      
result of these experiments1 as will be 
presently explained1 has  shown         
satisfactorily that it is more          
profitable to keep up the  distillatory 
process for a period of eight hours1    
with the retorts fully  charged1 than to
 abridge the operation by terminating it
 at the end of  six hours4    ,others   
again1 have imagined1 that it would be  
more economical to  decompose a less    
quantity of coal at once1 or to decrease
 the thickness  of the stratum of coal  
in the cylindrical1 or in any of the    

before named  retorts2 but then again1  
serious difficulties occur in the       
practice4  ,the more frequent charging  
of the retorts and luting on the        
covers1#af  which such a mode of        
operating require1 occasions a          
prodigious waste of  fuel1 time and     
labour4 ,a greater number of retorts and
 more workmen must  likewise be         
employed1 in order to produce the       
requisite quantity of gas  daily1 which 
the manufacturer is called upon to      
supply2 more space of  ground is        
required1 and more dead capital must be 
sunk in the  establishment4 ,the more   
frequent and sudden alterations of      
temperature  which the retorts          
necessarily suffer1 by the more frequent
 introduction  of cold coal1 renders    
them extremely liable to become injured2
 and it is  almost impossible to        
maintain a number of retorts thus       
worked1 at an  uniform temperature4     
#af ,when the cover is ground on1       
air-tight1 the cost of the retort is    

much increased4    ,from various        
statements1 which ,i have been favoured 
with1 in  confirmation of my own        
observations on the best method of      
working  cylindrical retorts1 it may    
suffice to lay before the reader the    
result  of a series of operations       
instituted by one of the largest and    
best  conducted establishments in this  
country2 the public-spirited and        
indefatigable directors of which have   
done more in the way of extensive1      
costly1 varied and long continued       
experiments1 to improve the new art of  
lighting with gas1 than any other       
similar body in the kingdom2 and        
without whose exertions the gas light   
illumination would never have  reached  
the state of perfection it has attained4
      ,report on a course of            
,experiments made to ascertain the      
comparative  ,economy#ag of             
manufacturing every week1 #heg1ffg cubic
 feet of gas1 by  means of ,cylindrical 
,retorts variously worked4      #ag ,the

 cost of materials and price of labour  
in this estimate1 as    well as in all  
subsequent statements1 is given such as 
they actually    were1 at the time1 when
 the experiments to which they refer    
were made4      ,gas ,light and ,coke   
,company's ,works1    ,westminster      
,station4      ,february #hth1 #ahai4   
,,sir1    ,enclosed are the result of a 
series of experiments made under my     
direction with a view of ascertaining   
the relative value of the  different    
modes of working cast-iron cylindrical  
retorts1 from which  you will perceive  
that it is more economical to work eight
 hours  charges1 as the workmen call it1
 that is to say1 to suffer the          
distillatory process to go on for eight 
hours1 when nearly two bushels  of coal 
are contained in each retort1 than to   
discontinue the operation  at the end of
 six hours4      ,i am with respect1    
,sir1 ,yours1 c4    ,t4 ,s4 ,,peckston4 
,to ,mr4 ,f4 ,accum1    ,compton        
,street1 ,soho4      ,process ,a4       

,number of,number                       
,quantity,quantity    ,days the   of    
,quantity of ,coal  ,quantity of      of
    of ,gas     ,retorts ,retorts       
decomposed for    ,coal used       ,gas 
from one      were     in    obtaining  
,gas4    for ,fuel4      pro-  ,chaldron
     worked4 action4                    
duced4 of ,coal4                        
----------------------------------------
-------------------------               
,chal- ,bushel4,chal- ,bushel4 ,cubic   
,cubic                    dron4         
dron4            ,feet4 ,feet4          
,monday     #hg     #aj       #cj       
#d       #bd     #id1ihg  #h1gfh        
,tuesday    #hh     #ad       #bd       
#f        #h    #abh1eig  #h1ghd        
,wednesday  #hh     #ad       #bd       
#f        #h    #abb1ahh  #h1cca        
,thursday   #id     #ae       #bd       
#f       #bf    #aca1agf  #h1cgc        
,friday     #if     #af        #j       
#f       #cb    #abg1fif  #g1iha        
,saturday   #if     #af        #j       

#f       #bj    #abg1ecf  #g1iga        
,sunday     #if     #ae       #ah       
#f        #d    #abe1dhg  #h1jib        
----------------------------------------
---------                     #ajc      
#ab     #dc       #ad    #heg1ffgh1cjjah
          #ah ,average proportion of gas
 from a chaldron of coal4               
,expenditure of ,process ,a4            
,coals1 decomposed1 #ajc chaldron #ab   
bushel1 at  #b4 #aas4    #f;d4 the      
chaldron1 7#bg ,cwt47                   
#bff  #b #j      ,small ,coal1 #dc      
chaldron1 #ad bushels1 used for fuel1 at
  #b4    #bs4 the chaldron              
#ia  #b #d      ,wages of two additional
 workmen 7not required had the          
retorts been worked at eight hours      
charges17 at  #a4 #afs4    each man1 the
 week                                   
#c #ab #j                               
-----------                             
,total expenditure1 4 #cfj #ag #j       
,products of ,process ,a4      ,coke1   
#ajc chaldron1 #ab bushel1 at  #a4 #gs4 

the chaldron    #aci #aj #j             
,breeze1 or small coke1 #f chaldron1 #i 
bushels1 at #ahs4 the    chaldron       
#e #ab #f      ,tar1 #g tons1 at  #f4   
the ton                                 
#df #aj #j      ,ammoniacal liquor1     
#ahfd gallons1 at #a;d4 the gallon      
#aa #ac #j      ,gas1 #heg1ffg cubic    
feet1 at #aes4 the thousand cubic feet  
#fdc #e #j                              
----------    ,total for products1      
#hdf #aj #f    ,hence the amount of     
expenditure for procuring #heg1ffg cubic
 feet of gas1  is  #cfj4 #ags4    ,the  
value of the saleable products  #hdf4   
#ajs4 #f;d4    ,and the average         
proportion of gas obtained from one     
chaldron of  ,newcastle coal1 #h1cjj    
cubic feet4      ,process ,b4           
,number of ,number                      
,quantity  ,propor-    ,days the    of  
,quantity of ,coal   ,quantity of     of
    tion of     ,retorts ,retorts       
decomposed for     ,coal used     ,gas  
,gas to a      were      in   obtaining 

,gas4     for ,fuel4     pro-           
,chaldron     worked4 action4           
duced4 of ,coals4                       
----------------------------------------
-------------------------               
,chal- ,bushel4,chal- ,bushel4  ,cubic  
,cubic                    dron4         
dron4            ,feet4 ,feet4          
,monday     #eg      #i       #ah       
#b      #ac      #id1ihg #aj1jjj        
,tuesday    #gg     #ab       #ca       
#c       #h     #abh1eig #aj1jjj        
,wednesday  #gc     #ab        #h       
#c       #b     #abb1ahh #aj1jjj        
,thursday   #gi     #ac        #d       
#c      #aj     #aca1agf #aj1jjj        
,friday     #gf     #ab       #bg       
#c       #g     #abg1fif #aj1jjj        
,saturday   #gg     #ab       #bg       
#c       #f     #abg1ecf #aj1jjj        
,sunday     #gf     #ab       #bj       
#c       #f     #abe1dhg #aj1jjj        
----------------------------------------
---------                     #ajc      
#ab     #ba      #af     #heg1ffg       

#aj1jjj                                 
#ai          #ai ,average proportion of 
gas from a chaldron of coal4            
,expenditure of ,process ,b4      ,coal1
 decomposed1 #he chaldron1 #bg bushels1 
at  #b4    #aas4 #f;d4 the chaldron     
#bbj #af #aj      ,small ,coal1 #ba     
chaldron1 #af bushels1 used for fuel1 at
     #b4 #bs4 the chaldron              
#de  #j  #h                             
---------------    ,total expenditure1  
4 #bfe #ag  #f    ,products of ,process 
,b4      ,coke1 #ajj chaldron1 at  #a4  
#gs4 the chaldron              #ace  #j 
#j      ,breeze1 or small coke1 #c      
chaldron1 at #ahs4 the chaldron      #b 
#ad  #j      ,coal tar1 #f ,tons1 #h    
,cwt4 at  #f4 the ton                   
#ch  #h  #j      ,ammoniacal liquor1    
#aecf gallons1 at #a;d4 the gallon      
#i #ab  #j      ,gas1 #heg1ffg cubic    
feet of1 at #aes4 the thousand cubic    
feet                                    
#fdc  #e  #j                            
------------    ,total for products1    

4 #hbh #ai  #j    ,from the result of   
this process it appears1 that at the    
expence of  #bfel4 #ags4 #f2 the value  
of the products obtained is  #hbh4 #ais4
    ,by comparing the two preceding     
processes1 ,a and ,b1 it will be        
observed  that the same quantity of gas 
was generated each day1 notwithstanding 
there were fewer retorts in use1 and    
less coal decomposed by process ,b1     
than by ,report ,a1 and that the expence
 of fuel1 when the distillatory  process
 was continued for a term of eight      
hours1 was considerably less4  ,also1   
that the proportion of gas obtained from
 a chaldron of coals1 was  greater than 
when the process was continued for only 
six hours4    ,hence1 if from the       
products of                             
process ,a1 4 #hdf #aj #f    we take the
 products of process ,b1 4 #hbh #ai #j  
-----------                     ,the    
difference is1 4 #ag #aa #f    which1   
being subtracted from the difference    
between the expenditure1 as  specified  

in the process alluded to1 namely       
,process ,a1             4 #cfj #ag  #j 
,process ,b1                #bfe #ag  #f
                                        
---------------    ,the difference is   
4 #id #ai  #e                           
,less    #ag #aa  #f                    
---------------    ,and leaves a balance
 of 4 #gg #ag #aa    in favour of       
working eight hours charges1 for one    
week1 and producing  a like quantity of 
gas1 as had been obtained by working six
 hours  charges4    ,thus1 having       
compared the quantity of coals actually 
used when working  six hours charges1   
with what was used to produce a like    
quantity of gas  from eight hours       
charges1 ,i shall next point out1 in    
process ,c1 the  quantity of gas        
obtained when working the same number of
 retorts for a  period of eight hours   
which had been worked at the process of 
six  hours4      ,process ,c4           
,number of ,number                      
,quantity,propor-    ,days the  of      

,re-,quantity of ,coal   ,quantity of   
of ,gas tion of     ,retorts  torts     
decomposed for     ,coal used      pro- 
,gas to      were     #bj  obtaining    
,gas4       ,fuel4       duced4 a ,chal-
     worked4    in                      
dron of             action4             
,coals4                                 
----------------------------------------
-------------------------               
,chal- ,bushel4,chal- ,bushel4  ,cubic  
,cubic                    dron4         
dron4            ,feet4 ,feet4          
,monday      #hg    #af      #ah        
#c    #bb      #afe1jjj #aj1jjj         
,tuesday     #hh    #ad      #bd        
#c    #bd      #adf1ffg #aj1jjj         
,wednesday   #hh    #ad      #bd        
#c    #bd      #adf1ffg #aj1jjj         
,thursday    #id    #ae      #bd        
#c    #cc      #aef1fff #aj1jjj         
,friday      #if    #af       #j        
#d     #j      #afj1jjj #aj1jjj         
,saturday    #if    #af       #j        
#d     #j      #afj1jjj #aj1jjj         

,sunday      #if    #ae      #ah        
#c    #cb      #aee1jjj #aj1jjj         
----------------------------------------
---------                     #ajg      
#j        #bf    #bg    #a1jgj1jjj      
#aj1jjj                                 
#ba          #bj ,worked at six hours   
charges in process ,a1 page #he1 but    
here    worked at eight hours charges4  
#ba ,average proportion of gas from a   
chaldron of coal4    ,expenditure of    
process ,c4      ,coal decomposed1 #ajg 
chaldron1 at  #b #aas4 #f;d4 the        
chaldron                                
#bge #aj #f      ,small coal1 #bf       
chaldron1 #bg bushels1 used for fuel1 at
  #b    #bs4 the chaldron               
#ef  #c #f                              
----------    ,total expenditure        
#cca #ad #j    ,products of process ,c4 
,coke1 #abd chaldrons1 at  #a #gs4 the  
chaldron            #afg  #h #j         
,breeze1 or small coke1 #d chaldrons1 at
 #ahs4 the    chaldron                  
#c #ab #j      ,tar1 #h tons1 at 4 #f   

the ton                                 
#dh  #j #j      ,ammoniacal liquor1     
#aide gallons1 at #a;d4 the gallon      
#ab  #c #a      ,gas1 #a1jgj1jjj cubic  
feet1 at #aes4 for a thousand cubic     
feet                                    
#hjb #aj #j                             
-------------    ,total for products    
#ajcc #ac #a      ,,recapitulation4     
,products by process ,c4         #ajcc  
#ac #a      ,products by process ,a4    
#hdf #aj #f                             
-------------    ,difference            
#ahg #b #g      ,expenditure by process 
,a4       #cfj #ag #j      ,expenditure 
by process ,c4        #cca #ad #j       
----------    ,difference               
4 #bi  #c #j    ,from the above         
recapitulation it will appear1 that by  
working equal  numbers of retorts1 at   
six and at eight hours charges1 the     
balance is  considerably in favour of   
the latter method2 for1 from the        
foregoing  statement1 there appears to  
be on the practice of the latter method 

an  increase of saleable products       
amounting to                            
#ahg  #b #g                obtained at  
#bi  #c #j    less expence2             
consequently there is a  -------------  
balance of                 #baf #e #g in
 favour of    working the retorts1 as   
stated in process ,c1 over that method  
shewn in  process ,a2 and in such       
proportion1 let the number of retorts   
worked be  what it may1 an advantage    
will always be gained in this mode of   
manufacturing coal gas1 by working the  
retorts at eight hours charges1  as the 
workmen call it1 in preference to       
adopting the shorter process4    ,from a
 series of operations made#bb with      
twenty parallelopipedal and  with twenty
 cylindrical retorts1 worked for one    
month1 it has been  ascertained that the
 decomposition of coal is most          
economically  conducted when each retort
 is charged with #ajj pounds of coal1   
and the  distillatory process be        
continued for eight hours4 ,two men1 one

 by day  and one by night1 can attend   
nine or ten retorts4      #bb ,by ,h4   
,morrison1 ,esq4 and ,self2 the coal    
used1 was ,newcastle    7,bewick and    
,craister's ,walls ,end7 coal4          
,,part ,,vi4      ,temperature best     
adapted for working ,cylindrical        
,retorts4    ,there is perhaps no       
subject in the art of manufacturing coal
 gas1 on  which practical men are less  
agreed1 than they are on the temperature
  most economically to be employed for  
the production of coal gas in the  large
 way4 ,it must be sufficiently evident1 
that cast-iron retorts1 when  worked at 
a low temperature1 will last longer1    
than when exposed to  higher degrees of 
heat4#bc ,hence1 according to some      
operators1 the  economy of the process  
consists in saving the retorts1 at the  
expense of  a diminution1 even though   
considerable1 in the quantity of gas    
obtained2 whilst1 according to others1  
it is more economical to obtain  the    
largest possible quantity of gas at the 

expence of any consequent  injury to the
 distillatory vessel4      #bc ,it is   
essential that the retorts should be    
kept in constant    action night and    
day1 or at least never allowed to go    
below a red    heat4 ,the first portion 
of oxide which forms upon the surface1  
when    allowed to cool1 cracks and     
falls off1 leaving a new surface to be  
acted upon the next time it is heated4  
,by thus being every day heated    and  
cooled1 a retort will be speedily       
destroyed4    ,the truth appears to be  
wholly with neither of these extremes1  
nor  indeed in any absolute general rule
 which can be ventured on the  subject4 
,the degree of temperature proper to be 
adopted in gas works1 where the  method 
of decomposing coal in masses1 or layers
 from four to eight  inches in          
thickness1 and upwards1 is practised by 
means of the cast-iron  retorts1 of     
which a description has been given1 p4  
#ec1 chiefly depends  on circumstances  
of a local nature1 with regard to the   

price of coal and  labour1 so that where
 in one place it may be more profitable 
to employ a  very high temperature for  
the production of the gas1 it may be in 
others  quite the reverse4    ,the      
utmost therefore that can be done on    
this head1 is to state what  these      
circumstances are1 and to shew the value
 which belongs to them  under every     
supposable situation4    ,in this       
metropolis1 and in all other places     
where coal and labour bear a  higher    
price than probably elsewhere in this   
country1 and where saving  of time is   
also an object of primary importance1 it
 is clearly  established1 that the      
manufacturer who pursues the method of  
decomposing  coal in masses from five to
 eight inches and upwards in thickness1 
by  means of cast-iron retorts1#bd will 
consult his interest best1 by  employing
 such a high temperature for the        
decomposition of the coal1 as  will     
produce in the shortest time the        
greatest possible quantity of gas1  from

 a given quantity of coal1 without      
regarding the unavoidable  deterioration
 of the retorts4 ,but in places where   
coal and labour is  cheap1 it will be   
his interest to save the retorts at the 
expence of the  coal4 ,but that this    
fact may not rest on mere general       
assertion1 ,i shall  subjoin for the    
satisfaction of the reader a few        
statements of  experiments made upon a  
large scale for the purpose of          
ascertaining  these facts4      #bd ,the
 ,retorts should be manufactured of what
 is called in commerce1    iron of the  
second process4 ,the best cast-iron of  
this kind1 is of a    light grey colour1
 its fracture is granulated and dull1 it
 receives a    dent from the blow of a  
hammer4 ,the cast-iron which exhibits a 
dark    grey or black colour inclining  
to blue1 and presents granular          
concretions1 readily friable1 and       
therefore unfit for vessels intended    
to stand a long continued heat4         
,annual ,creditor and ,debtor ,account  

of manufacturing daily from #ej1jjj  to 
#ajb1jjj cubic feet of gas at the price 
which coal bears in the                 
metropolis4--,the operation being       
commenced with new ,retorts1 and the    
retorts being left in a fit working     
state4    ,the first of the following   
processes was conducted on the principle
 that  coal and labour1 being of an high
 price1 as in ,london1 it is most       
economical to obtain the greatest       
possible quantity of gas from a given   
quantity of coal in the least possible  
time1 without any regard to the  injury 
done to the distillatory vessel4    ,the
 second process is intended to          
illustrate the correctness of that      
principle1 by shewing that where coal   
and labour are at the high prices       
stated in the first process1 it is a    
losing system to work the retorts  at a 
lower temperature1 in order to make them
 last longer4    ,in some respects a    
similarity will be observed between     
these  experiments1 and those already   

given in page #he1 but besides their    
having reference to the separate and    
distinct circumstance of the high       
prices of coal and labour in ,london1 it
 will be found that they also  differ   
from the former statements1 in          
exhibiting1 not merely the expence  of  
working1 but the original cost of       
erecting the retorts1 as well as  the   
expence of replacing them4      ,process
 ,i4    ,the quantity of gas to be      
supplied each night1 was #ej1jjj cubic  
feet4    ,in order to produce this      
quantity1 thirty cylindrical retorts1   
each  containing two bushels of         
,newcastle coal1 were put in action4    
,the  temperature at which the retorts  
were worked1 was a bright cherry        
redness1 at which they produced at the  
rate of ten thousand cubic feet  of gas1
 from a chaldron of ,newcastle coal4    
,to work the retorts1 three workmen by  
day and three by night1 were  required4 
,the retorts were charged three times   
every twenty-four hours4 ,the first     

total expence of erecting the retorts1  
was 4 #bc each1 and it was found1  that 
when worked night and day1 they could   
not1 with the utmost care1  be made to  
continue fit for use for more than from 
five to six months2  hence1 a double set
 of the original number of retorts was  
requisite each  year4    ,the whole     
annual operation pursued on this plan   
stood as follows3      ,cost of sixty   
retorts1 thirty at work and thirty to   
spare1 with brick-work foundation1 iron 
coke hearth1    perpendicular pipe      
connected with hydraulic main1 see ,p1  
fig4 #b1 plate ,,iv41 at  #bc4 each4    
4 #achj  #j #j      ,six workmen1 three 
during day-time1 and three at night1    
at  #a4 #fs4 each the week              
#dje #ab #j      ,coals1 #ahbe chaldron1
 requisite for producing the gas1    at 
#b4 #hs4 the chaldron                   
#dchj  #j #j      ,wear and tear of     
grate bars1 fire-shovels1 tongs and     
rackers                                 
#db  #j #j      #def chaldron of ,coal  

for fuel1 4 #b #as4 the chaldron  4 #ice
  #f #c                                 
------------    ,total expence1         
4 #gadb #ah #c      ,subtract the market
 price of saleable    ,coke#be produced 
by the process1 viz4 #ahbe    chaldron1 
at  #a4 #cs4 the chaldron        4 #bjih
 #ae #j      #def chaldron of small     
,coke or ,breeze1 at    ten shillings   
the chaldron                      #bbh  
#b #f                                   
------------     #bcbf #ag #f           
------------    ,there remains          
4 #dhaf  #j #i    for the annual expence
 of maintaining the apparatus on this   
construction4      #be ,the tar and     
ammoniacal liquor afforded by the       
process1 not being    always saleable   
articles1 are omitted to be charged in  
the estimates4      ,process ,,ii4      
,the next experiment made was1 to       
ascertain the contrary practice of      
operating1 namely the mode of working   
the retorts1 on the principle  which    
holds out1 that it is more economical to

 be satisfied with a less  quantity of  
gas than what the coal is capable of    
furnishing1 because by  so doing the    
retorts become less deteriorated and    
remain for a longer  time in a state fit
 for use4    ,the quantity of gas to be 
supplied each night1 was1 as in the     
preceding  process1 fifty thousand cubic
 feet4    ,the number of retorts        
required to produce that quantity1 was  
forty-two1  and to make them last twelve
 months instead of six months1 as in the
  preceding process1 it was necessary to
 work them at a temperature1 at  which a
 chaldron of coal produces from seven   
thousand1 to eight thousand  cubic feet 
of gas4    ,the result of this operation
 was as follows3      ,cost of forty-two
 retorts1 with brick-work foundation1   
cast-iron coke hearth1 perpendicular dip
 pipe1 connected    with the hydraulic  
main1 at 4 #bc each                     
4 #iff  #j #j      ,eight workmen1 four 
by day and four by night1 at  #a4       
#fs4 each the week                      

4 #edj #af #j      #beee chaldron of    
,coal1 requisite for producing the gas1 
at 4 #b #hs4 the chaldron               
4 #fabc  #j #j      ,wear and tear of   
grate bars1 fire shovels1 tongs and     
rackers                                 
#db  #j #j      #fch chaldron of ,coal  
for fuel1 at  #b4 #as4 the    chaldron  
#acjg #ah #j                            
------------                            
4 #higi #ad #j      ,deduct the market  
price of #beee chaldron    of coke1     
produced by the process1 at  #a4    #cs4
 the chaldron4                         4
 #bich  #e #j      #fch chaldron of     
small coke1 or breeze1    at #ajs4 the  
chaldron                            #cai
  #g #f                                 
------------  4 #cbeg #ab #f            
------------      ,there remains for the
 annual expence of maintaining the      
apparatus                               
4 #egbb  #a #f      ,subtract the annual
 expence of ,process ,i4                
#dhaf  #j #i                            

------------    ,the balance in favour  
of ,process ,i4 is                     4
 #ijf  #j #i      ,process ,a4    ,in   
the following additional processes1 the 
retorts when begun to be  worked1 were  
also new1 and were left in a fit working
 state4 ,the  quantity of gas required  
to be produced daily1 was #ajb1jjj cubic
  feet4#bf      #bf ,these ,experiments 
were made at the ,westminster ,gas      
,works1 under    the superintendance of 
,mr4 ,clegg1 to whom ,i am indebted for 
this    communication4    ,the retorts  
were worked at a temperature at which   
they produced #aj1jjj  cubic feet of gas
 from the chaldron1 7#bg ,cwt47 of      
,newcastle coal4      ,to sixty-eight   
retorts1 twice replaced1 at  #ae4 each  
4 #bjdj  #j #j      ,deterioration of   
grate bars1 fire shovels1 tongs1 and    
rackers                                 
#ia #af #j      #cgbc chaldron of coal  
for obtaining the gas1 at  #b4    #hs4  
the chaldron                            
#hice  #d #j      #icj chaldron1 #bg    

bushels of ,coal1 for fuel1 at  #b4     
#as4 the chaldron                       
#aijh  #j #i      #ad ,men at  #a4 #fs4 
each1 the week1 being #g for the    day1
 and #g for the night                   
#idf  #h #j                             
-------------                           
4 #ac1iba #h #i      ,deduct the market 
price of #cgbc chaldron    of saleable  
coke1 at  #a4 #cs4 the    chaldron      
4 #dbha  #i #j      #icj chaldron of    
small coke1 or breeze1    at #ajs4 the  
chaldron                          #dfe  
#g #f                                   
------------  4 #dgdf #af #f            
------------    ,cost of obtaining1     
#cg1bcj1jjj cubic feet of gas           
4 #iagd #ab #c      ,process ,b4        
,producing #hjjj cubic feet of gas1 from
 the chaldron of ,newcastle coal4       
,eighty-five retorts1 once replaced at 4
 #ae each          4 #abge  #j #j       
,deterioration of grate bars1 fire      
shovels1 tongs and    rackers           
#aag #af #j      #dfec chaldron of coals

 for obtaining the gas1 at  #b4    #hs4 
the chaldron                            
#aa1afg  #d #j      #aafc chaldron of   
coal for fuel1 at  #b4 #as4 the         
chaldron                                
#bche #ac #i      ,eighteen men at  #a4 
#fs4 each man the week1 being nine      
for the day1 and nine for the night     
#abaf #af #j                            
--------------                          
4 #af1afb  #i #i    ,from which deduct  
#dfec chaldron of    saleable ,coke1 at 
4 #a #cs4 the chaldron  4 #ecej #ai #j  
#aafc chaldron of small coke1 or breeze1
    at #ajs4 the chaldron               
#eha #ag #f                             
------------   4 #eicb #af #f           
--------------    ,cost of obtaining    
#cg1bcj1jjj cubic feet of gas1          
according to process ,b1                
4 #aj1bbi #ac #c      ,deduct the cost  
of ,process ,a1                         
#iagd #ab #c                            
--------------    ,balance in favour of 
,process ,a4                           4

 #ajee  #a #j    ,the reader will have  
no difficulty in calculating from the   
preceding  experiments1 every variation 
which can possibly take place1 as to the
  degree of temperature most            
economically to be employed in          
consequence  of a variation in the      
prices of coal1 coke and labour4#bg     
#bg ,the average cost at which coal gas 
can be manufactured on a large    scale 
in ,london1 is seven shillings the      
thousand cubic feet1 deducting    not   
only the interest of the capital sunk in
 erecting the    establishment1 rent and
 taxes1 the cost of the coal1 labour1   
wear and    tear of the machinery1 and  
superintendence1 but all other necessary
    and incidental expences that may    
occur4      ,comparative facility with  
which the decomposition of different    
species  of ,coal is effected4    ,the  
temperature necessary for the           
decomposition of different kinds of     
coal1 varies4 ,some species of coal are 
more readily decomposed1 and  require a 

less portion of fuel than others2 they  
yield up their maximum  quantity of gas1
 in an almost equal stream from         
beginning to end1 and no  extraordinary 
increase of temperature is required to  
terminate the  distillatory process4    
,other kinds of coal require a different
 treatment2  the temperature necessary  
to complete their decomposition requires
 that  the heat should be considerably  
increased as the process advances2 and  
without this condition the evolution of 
the gas would cease altogether4    ,a   
striking proof of this statement may be 
seen when ,newcastle or  ,sunderland    
coal are attempted to be decomposed at a
 temperature which is  sufficient for   
the decomposition of ,scotch ,splent    
coal1 or ,lancashire  ,wiggan coal4     
,the decomposition of the latter1 will  
be fully effected when the  distillatory
 vessel exhibits to the eye a dull      
cherry redness1 and the  evolution of   
the gas at such a temperature will take 
place in torrents  from beginning to    

end4 ,in order1 on the other hand1 to   
complete the  decomposition of          
,newcastle and ,sunderland coal1 the    
heat must be  increased as the process  
proceeds1 and the production of the gas 
will be  extended far beyond the time   
required for decomposing a like quantity
 of  ,scotch1 or ,lancashire ,wiggan    
coal1 when exposed to the same degree of
  heat4    ,it must be allowed1 however1
 that few experiments have been yet made
 on  this subject4 ,i have reason to    
believe that all those varieties of coal
  which afford an incoherent friable    
coke1 are decomposed at a much lower    
degree of heat1 than such as produce1   
when treated under like  circumstances1 
a ponderous compact coke4 ,and if we    
give credit to the  assertion of those  
workmen1 whose business it is to        
manufacture a given  quantity of gas by 
means of a certain quantity of coal     
delivered to  them1 it would appear that
 coal which affords gas abounding in    
sulphuretted hydrogen1 is the kind of   

coal most easily to be decomposed4      
,this1 as far as it regards the         
decomposition of ,scotch ,splent or     
cannel  coal1 is certainly true4 ,no    
species of coal affords gas at a lower  
temperature1 and of none is the gaseous 
product more loaded with  sulphuretted  
hydrogen gas4 ,the subject is important 
and deserves to be  pursued2            
particularly in places where coke is    
not1 as it is in the  metropolis1 and   
all places where coal bears a high      
price1 next to gas1  the primary article
 to which the attention of the          
manufacturer of coal  gas ought to be   
directed4    ,the following are the     
result of a series of experiments on the
 subject  made at the ,westminster ,gas 
,works1#bh the same temperature being   
employed throughout the process4        
#bh ,communicated by ,mr4 ,t4 ,s4       
,peckston4                 ,varieties of
 ,coal4                    ,ratio of    
time                                    
in ,decimals4    ,scotch ,splent or     

,cannel coal                            
#a1jj    ,newcastle coal1 7,nesham7     
#a1jd    ,gloucestershire coal          
,forest of ,dean first variety 7,low    
,delph7          #a1jh    ,newcastle    
coal1        ,second variety1 7,middle  
,delph7                    #a1ji        
,third variety1 7,heaton ,main7         
#a1ae        ,fourth variety1 7,brown's 
,wall's ,end7              #a1ah        
,fifth variety1 7,hutton's ,low main7   
#a1cj        ,sixth variety1 7,tyne     
,main7                        #a1ed     
,warwickshire coal1        ,first       
variety1                                
#a1fj        ,second variety1           
#a1fe        ,third variety1            
#a1fh          ,,part ,,vii4            
,horizontal ,rotary ,retorts1 lately    
brought into use for manufacturing  coal
 gas4    ,the many disadvantages        
attendant on the plan of decomposing    
coal in  masses from five to ten inches 
in thickness1 as already sufficiently   
exposed in the preceding parts1 had     

naturally the effect of developing a    
principle of manufacturing coal gas1    
which practice has now fully            
established1 namely3 that to decompose  
coal1 in thin layers from two to  four  
inches in thickness1 is to obtain the   
greatest quantity of gas from  a given  
quantity of coal at the least expence4  
,mr4 ,clegg was the first person who    
pointed out to the public the           
advantages that must accrue from this   
mode of operating1 and to him we  are   
indebted for the construction of an     
apparatus1 the great ingenuity  and     
superiority of which1 entitles what is  
called the horizontal rotary  retort1 to
 all the merit and praise that belongs  
to the character of an  original        
invention4    ,the numerous and great   
advantages of this distillatory         
apparatus1 the  rapidly increasing      
adoption of it1#bi and the almost       
certain prospect  which exists of their 
ultimately superseding all former       
methods of  decomposing coal1 make it   

proper that ,i should lay before the    
reader1 as  full an account as my limits
 will permit1 of the construction and   
operation of this retort1 and the mode  
of applying it2 and this becomes  the   
more necessary on account of the many   
important improvements which  the       
apparatus has undergone since its first 
adoption1#cj and of which  no           
description has yet been laid before the
 public4      #bi ,retorts of this      
description have been lately adopted1 in
 the ,gas    ,works at ,bristol1        
,birmingham1 ,chester1 ,kidderminster1  
and at many    other provincial ,gas    
,establishments4      #cj ,an account of
 the original construction of the rotary
 retort may    be seen in the           
,repository of ,arts1 ,no4 ,,clxxvi1    
#ahaf1 page ,i4 and also    in the      
,journal of ,science1 ,vol4 ,,ii4 page  
#acc4    ,the following account will    
render the construction of this retort  
sufficiently obvious3      ,description 
of the ,horizontal ,rotary ,retorts at  

the ,royal ,mint4#ca      #ca ,the      
retorts lately erected at the ,gas      
,works1 at ,birmingham1    ,chester1    
,bristol1 c4 are similar to those at the
 mint4    ,the horizontal rotary        
,retorts at the ,royal ,mint1 are hollow
 cylinders1  eight feet six inches in   
diameter and #ae inches high1 arched a  
little at  the top4 ,they are made of   
wrought-iron plates1 half an inch thick1
  rivetted together in the manner of a  
steam-engine boiler2 ,a1 ,a1 ,a1 fig4   
#b1 plate ,,iii4 exhibits a             
perpendicular section of the rotary     
retort4 ,in  fig4 #a1 plate ,,ii4 the   
retort is seen fixed in the brick-work2 
a1 fig4  #a1 plate ,,ii4 shews the mouth
 of the retort1 through which the coals 
are  introduced1 and from whence the    
coke is withdrawn4 ,it is also shown in 
perspective at ,b1 ,b1 ,b4 fig4 #b4     
plate ,,vii4 ,the mouth is closed with a
  cast-iron door fitted on air-tight by 
grinding4    ,the door is connected at  
its upper and lower extremities1 with a 

frame  and adjusting rod1 see ,b1 ,b1   
fig4 #a1 plate ,,ii41 and also plate    
,,vii41 by  means of which it may       
readily be slided down below the mouth  
of the  retort1 when the coals are to be
 introduced1 or coke is to be withdrawn4
  ,to the upper extremity of the rod ,b1
 fig4 #a1 plate ,,ii41 is fixed a       
lever1 loaded with a counterpoise weight
 ,c1 to balance the door1 and to  render
 the opening and closing of it easy and 
expeditious4    ,the mouth-piece and its
 door is three feet long1 and nine      
inches wide2  it projects nine inches   
beyond the brick-work or furnace in     
which the  retort is fixed1 as may be   
seen at fig4 #a1 plate ,,ii4    ,the    
fire-place1 which is on the opposite    
side to that of the mouth of  the       
retort1 heats only one-third part of the
 whole capacity of the  retort to that  
degree which is proper for the complete 
and rapid  decomposition of the coal1   
while the remaining parts1 which are not
 over  the fire-place1 and to which the 

fire flues do not extend1 are kept at a 
lower temperature4    ,the flues are    
directed under about one-third of the   
area of the bottom  of the retort1 and  
after having passed over one-third part 
of the area  of the top of the retort1  
they pass into the chimney4 ,fig4 #a1   
plate ,,vi41  exhibits the direction of 
the flues2 ,a1 ,a1 the flues1 and the   
fire-place4 ,the whole retort is guarded
 from the contact of the fire1  which   
would soon destroy it1 by fire-bricks2  
it notwithstanding speedily  receives   
the full effect of the heat1 and retains
 its temperature when  once heated for a
 long time4 ,fig4 #a1 plate ,,ii41      
exhibits one of the  retorts fixed in   
its furnace4 ,a perspective view of     
three retorts may be  seen in fig4 #b1  
plate ,,vii4    ,through the centre of  
the retort1 passes perpendicularly1 an  
iron shaft  ,d1 as shown in the section 
of the retort1 fig4 #b1 plate ,,iii41   
and also  in fig4 #a1 plate ,,ii4 ,the  
lower extremity of the shaft revolves   

upon the  bottom of the retort1 in a    
cup-shaped cavity1 while its upper      
extremity  passes through the roof of   
the retort1 where the latter is made    
air-tight by means of a pipe ,e1 fig4   
#a1 plate ,,ii41 and ,e1 fig4 #b1 plate 
,,iii41 closed at the top and           
surrounding the shaft1 and hence the    
shaft  must always preserve its centre4 
,to the lower extremity of the shaft is 
keyed a box or centre piece1            
7technically called a rose centre17 ,f1 
fig4 #b1 plate ,,iii4 ,it is also  seen 
in the perpendicular section of the     
retort1 fig4 #a1 plate ,,ii4 ,from  this
 shaft radiate twelve wrought-iron arms1
 ,g1 ,g1 fig4 #b1 plate  ,,iii41#cb     
fixed in sockets made in the box4 ,these
 arms are elevated  three inches above  
the bottom of the retort1 and extend to 
nearly within  its whole inner          
circumference4 ,they are wedge-shaped1  
and their greatest  diameter is at right
 angles to the base of the retort1 so   
that the  weight of the arms rests on   

the axis4 ,they are intersected by two  
concentric rings1 as will be seen on    
inspecting fig4 #e1 plate ,,iii41  which
 exhibits the plan of the retort1       
together with the iron arms1 ,g1  ,g1   
and concentric rings4 ,the centre of    
figure #e1 shows also the plan of  the  
rose centre ,f1 fig4 #b1 plate ,,iii41  
into which the arms are keyed4      #cb 
,in the horizontal rotary ,retorts at   
the ,chester1 ,birmingham and           
,bristol ,gas ,works1 which are twelve  
feet six inches in diameter1 there      
are fifteen arms4 ,at some ,gas ,works  
the arms are made of cast-iron4         
,between the arms are placed twelve     
shallow iron trays or boxes1 destined   
to contain the coal from which the gas  
is to be obtained4 ,they are  formed to 
the segment of a circle1 hence the whole
 series of them when  arranged in the   
retort1 exhibits a shallow circular     
tray1 which1 when  motion is given to   
the shaft1 may be made to revolve within
 the retort4    ,fig4 #ab1 plate ,,iii4 

exhibits one of the shallow trays1 or   
coal boxes in  perspective4    ,it will 
be obvious1 that by the motion of the   
shaft1 any number of the  trays or      
coal-boxes can readily be brought from  
the coldest1 into the  hottest1 and from
 the hottest into the coldest part of   
the retort4    ,h1 fig4 #a1 plate ,,ii41
 and a1 plate ,,iii41 or ,h1 plate      
,,vii41 is a  perpendicular pipe        
situated at the margin of the retort1   
close behind  the mouth-piece1 and      
consequently in the coldest part of the 
retort4 ,it  serves to carry off the    
distillatory products evolved from the  
coal1 and  causes part of the vaporous  
tar1 which becomes condensed in it1 to  
trickle back again upon the coal in the 
retort1 in order to become  converted   
into gas1 when the coal on which it     
falls becomes situated  over the        
fire-place4    ,this pipe is furnished  
at its upper extremity with a hydraulic 
valve1  ,j1 fig4 #a1 plate ,,ii4 ,it    
consists simply of an inverted cup ,x1  

applied  over the upper open extremity  
of the perpendicular pipe ,h1 and       
submersed  into a cup formed of a       
portion of larger pipe1 surrounding the 
pipe ,h1  containing tar4 ,the smaller1 
or inner cup ,x1 is represented in the  
design raised out of the liquid         
contained in the outer cup ,j1 to show  
an  aperture ,y1 made in the smaller or 
inner cup2 the use of which will be     
mentioned hereafter4 ,the inverted cup  
,x1 is furnished with a chain1 one      
extremity of which is fastened to the   
upper extremity of the cup1 the  other  
passes over a small wheel1 and descends 
through the roof of the  building1 as   
shown in the design4    ,k1 fig4 #a1    
plate ,,ii41 or ,k ,k1 fig4 #b1 plate   
,,vii41 is a branch pipe  proceeding    
laterally from the perpendicular pipe   
,h2 it communicates with  the hydraulic 
box ,l1 fig4 #a1 plate ,,ii4 ,n1 is a   
pipe which proceeds from  the hydraulic 
box ,l2 it serves to carry away the     
gaseous and liquid  products to their   

places of destination4 ,the liquid      
products1 namely1  the tar and          
ammoniacal fluid1 become deposited in   
the tar cistern1 fig4  #c1 plate ,,ii41 
into which the pipe ,n terminates4 ,the 
tar cistern is  furnished with two      
floats ,y ,y2 the one serves to indicate
 the quantity  of tar1 and the other the
 quantity of aqueous ammoniacal fluid   
contained  in the vessel4 ,these fluids 
may be drawn off without admitting air  
into  the vessel by the stop-cock and   
bent tube1 exhibited in the figure4     
,the shorter pipe ,n1 which proceeds    
from the tar cistern1 fig4 #c1 plate    
,,ii41 and communicates with the        
purifying apparatus or lime machine1    
fig4  #b1 plate ,,ii41 serves to convey 
the gaseous fluid1 which accompanied the
  condensible liquids deposited in the  
tar cistern1 back again into the  lime  
machine1 or purifying apparatus1 fig4   
#b1 plate ,,ii41 the  construction of   
which1 together with the conveyance of  
the gas from this  vessel to its place  

of destination will be stated hereafter4
    ,l1 fig4 #a1 plate ,,ii41 or fig4   
#b1 plate ,,vii41 is an iron flap table1
  placed level with the bottom of the   
mouth of the retort4 ,it is  convenient 
to hold several coal trays ready charged
 with coal in a state  fit to be        
introduced into the retort4    ,the     
fire-place1 flues1 and ash-pit of the   
furnace1 in which the retort  is fixed1 
are sufficiently obvious by mere        
inspection of fig4 #a1 plate  ,,ii4 ,the
 front elevation of the retort is seen  
in fig4 #b1 plate ,,vii41  which        
exhibits three horizontal retorts2 two  
of which have the door of  the          
mouth-piece slided down1 and one with   
the door in its place1 or  shut4 ,the   
circular ring seen in this design1 at   
the top of each retort1  which rests on 
iron-bearing bars1 the extremities of   
which are let into  the end walls of the
 furnace1 serves to support the roof of 
the retort  by means of bolts1          
proceeding from the inner side of the   

roof4 ,this  arrangement is likewise    
shown in the section1 fig4 #a1 plate    
,,ii4#cc ,at  the bended part of the    
perpendicular pipe ,h1 fig4 #a1 plate   
,,ii41 is seen  a bonnet1 or cover1     
which closes an opening made into the   
pipe ,h1  through which1 by means of an 
iron rod1 the lower extremity of the    
pipe  ,h1 may1 from time to time1 be    
examined1 to guard against an           
incrustation  of decomposed tar or      
carbonaceous matter that might happen to
 accumulate  in that part of the pipe4  
,the upper part of the pipe ,h1 above   
the bonnet  at the bended part1 requires
 no examination4      #cc ,a more       
economical method of supporting the roof
 of the retort has    lately been       
adopted by ,mr4 ,clegg4 ,it consists in 
giving the roof the    form of an       
inverted arch1 supported on the         
,catenaria plan1 by two    bolts only1  
placed at the most elevated extremity of
 the arch and    secured to an          
horizontal beam4    b1 fig4 #b1 and b1  

fig4 #e1 plate ,,iii41 is the flanch of 
the retort2  c1 fig4 #b1 plate ,,iii41  
the flanch of the mouth-piece2 d1 the   
cutter1  or wedge1 which draws the      
mouth-piece close2 e1 the cross bar1    
against  which the cutter d1 bears1 to  
render the mouth-piece air tight2 f1    
fig4 #b1 one of the eye-bolts or arms   
which support the cross bar e2 it  is   
also seen at e1 in the plan of the      
retort1 fig4 #e1 plate ,,ii4 ,in  this  
figure b is the flanch of the retort1   
and c the door4    ,these few           
particulars will be sufficient to enable
 the reader to  understand the          
construction of the retort2 its action  
is as follows4      ,action and         
,management of the ,horizontal ,rotary  
,retort4    ,when the retort is heated  
to the proper temperature for the       
decomposition of the coal1 the door is  
slided down1 and the coal boxes  charged
 with small coal are slided into the    
retort from the table1 ,l1  fig4 #a1    
plate ,,ii41 one by one1 so that each   

box rests firmly upon the  concentric   
rings placed between the arms of the    
retort2 the door is then  slided up     
again into its place and rendered       
air-tight by means of  wedges4    ,when 
the whole circle fig4 #e1 plate ,,iii4  
is thus filled with  coal-boxes1 7the   
coal should be spread in the boxes1 in  
layers two or  three inches in depth17  
it is obvious that of all the twelve    
boxes1 four  only can be situated       
directly over the fire-place1 while the 
remaining  eight are placed right and   
left towards the door of the retort4    
,the coal  in the former boxes receives 
the full effect of the heat1 7see the   
plan  of the fire flues of the retort1  
fig4 #a1 plate ,,vi417 while the        
remaining  eight boxes to which the fire
 does not extend1 are less heated4 ,the 
coal  in the four boxes which are in the
 hottest part of the retort becomes     
rapidly decomposed1 whilst the coal in  
all the other boxes is gradually        
heated1 and consequently deprived only  

of moisture1 previous to being          
subjected to the greatest heat4 ,the box
 which is situated under the  condensing
 pipe ,h1 plate ,,ii41 near the entry   
door1 receives the  condensed tar which 
trickles down the pipe ,h4    ,now let  
us suppose that the coal in the four    
boxes over the fire place  is fully     
decomposed1 which will be the case if   
#cb pounds of coal are  in each box1 in 
two hours1 the workman then turns the   
shaft ,e1 fig4 #a1  plate ,,ii41        
one-third part of the circumference of a
 circle1 by pulling  towards him by     
means of an iron hook the nearest iron  
arm that may  happen to be opposite to  
the door2 this moves those boxes which  
at the  commencement of the operation   
were over the fire-place1 towards the   
coldest part of the retort1 namely1     
towards the door which is opposite  to  
the fire-place1 and a second series1 or 
four of the adjacent boxes1  are brought
 in turn into the hottest part of the   
retort1 or over the  fire-place1 from   

whence the preceding boxes were removed4
    ,when the coal in the second series 
of boxes has been two hours in the      
hottest part of the retort1 its         
decomposition will be completed2 the    
workman therefore turns the shaft again 
one-third part of a circle1 and  a third
 series advances in their place1 while  
at the same time the first  series      
becomes situated opposite the entry door
 of the retort1 from  whence they may be
 withdrawn and exchanged for an extra   
set of trays1  ready charged with coal  
and placed on the iron table for that   
purpose4    ,in this manner the         
operation proceeds4 ,one-third part of  
the whole  charge of coal within the    
retort is always in the act of becoming 
decomposed2 another third part is       
gradually heated1 and totally deprived  
of moisture1 previous to its being      
exposed to the temperature necessary    
for its decomposition2 and the remaining
 third part placed in the  coldest part 
of the retort1 receives that portion of 

tar1 which escapes  decomposition1 and  
trickles down the perpendicular pipe1 in
 order to be  decomposed when the coal  
upon which it falls becomes situated    
over the  fire-place4 ,hence the        
quantity of tar obtained from one       
chaldron of  ,newcastle coal1 when      
decomposed by means of an horizontal    
rotary retort1  seldom amounts to more  
than sixty or seventy pounds1 whereas   
the same  quantity of coal when         
decomposed by means of cylindrical or   
parallelopipedal retorts1 yields never  
less than from one hundred and  fifty1  
to one hundred and eighty pounds4 ,an   
horizontal rotary retort1  twelve feet  
six inches in diameter1 and fifteen     
inches high1 furnishes  in the ordinary 
way of working every twenty-four hours1 
fifteen thousand  cubic feet of gas1    
when five trays of the retort are       
charged with three  bushels of          
,newcastle coal4 ,the weight of the     
retort is three tons2 its  capacity1 one
 hundred and fifty cubic feet4    ,the  

hydraulic valve described page #aaf1    
serves merely to restore the            
equilibrium1 between the gas within the 
retort1 and the atmospheric air         
without1 previous to the opening of the 
door of the mouth of the retort4  ,to   
effect this the workman raises the cup  
,x1 by means of the chain1 so  that the 
small hole ,y1 in the cup ,x1 becomes   
raised out of the tar in  the cup ,l1   
and he closes it again when the retort  
is charged3 this  operation requires two
 minutes4 ,we have stated already1 that 
the door of  the retort is ground       
air-tight1 and hence it requires no     
luting4      ,advantages of the method  
of manufacturing ,coal ,gas by means of 
,horizontal ,rotary ,retorts4    ,the   
advantages of the mode of manufacturing 
coal gas by means of  horizontal rotary 
retorts1 consist in a saving of fuel1   
time1 labour1  and machinery1 a gain in 
the quantity of gas1 and increase in the
  quantity of coke4    ,saving of       
fuel4--,the mass of coal subjected to   

decomposition being  reduced from the   
dimension required in the old plan 7by  
means of  cylindrical retorts7 to the   
narrowest available limits1 there being 
no  outward crust of coke to be kept red
 hot for hours to no purpose1 while  the
 decomposition of the interior mass of  
coal is going on2--the coke  itself     
being as soon as formed removed from the
 source of heat1 and  applied while     
cooling1 to warm up a fresh supply of   
coal next in order  of becoming         
decomposed1 instead of being discharged 
in a red hot state1  into the open air1 
as requires to be done in the practice  
before  detailed--the whole fuel in     
short being necessarily and beneficially
  expended--the saving of coal employed 
as fuel in this respect1 is  exactly the
 gaining of all that is lost on the plan
 of employing  cylindrical or any of the
 retorts before described4 ,hence one   
chaldron  of coal is decomposed at the  
gas establishments where horizontal     
rotary  retorts are in action by means  

of twenty per cent of fuel1 and at some 
establishments an expert stoker will    
work the retorts with fifteen per  cent 
of fuel4    ,saving of time4--,the      
saving of time does not merely amount to
 what is  consequent on the speedier    
decomposition of the coal1 and the      
saving of  that heat which formerly     
required to be kept up a length of time 
to no  adequate purpose2 it also        
includes all that is gained in          
consequence of  the revolving motion to 
which the coal is submitted1            
superseding1 as has  been already       
mentioned1 the necessity of discharging 
the coke in an  ignited state from the  
retort4    ,when the coke is removed1 as
 previously explained1 page #gb1 red hot
 from  the cylindrical1                 
parallelopipedal1 semi-cylindrical or   
ellipsoidal  retorts1 the charging of   
the distillatory vessel with fresh coal 
produces such a sudden reduction of     
temperature1 that from three to four    
hours inevitably elapse before the      

retort is again in a full working       
state1 and to this circumstance the     
workmen 7perhaps very justly7  attribute
 the frequent sudden injury which the   
distillatory cast-iron  vessel sustains4
    ,another striking advantage of the  
new mode of decomposing coal is1 that   
besides saving the time which is wasted 
in keeping up an intense  temperature   
unnecessarily the revolving apparatus   
prevents entirely the  loss occasioned  
by these three or four hours of         
unnecessary cooling of  the distillatory
 vessel4 ,for each series of trays1 or  
coal boxes1  containing the ignited     
coke1 of the horizontal rotary retort1  
being  suffered to cool within the      
retort before the coke is discharged1   
and  being placed in contact with a     
fresh supply of coal1 the temperature of
  the retort is kept up uniformly the   
same from beginning to end4    ,saving  
of ,labour4--,in consequence of the     
superior facility with which  the mode  
of decomposing coal in thin layers and  

removing the coke as  fast as it is     
formed is effected1 the saving in point 
of labour is very  great4 ,the charging 
and discharging of the retort is        
performed in two  minutes4 ,hence one   
chaldron of coal may be decomposed by   
means of three  horizontal rotary       
retorts1 each twelve feet six inches in 
diameter1 and  with the attendance of   
two men1 in eight hours1 and produces   
from  fifteen thousand1 to eighteen     
thousand cubic feet of gas1 whilst ten  
thousand cubic feet of gas can only be  
obtained from the same quantity  of coal
 in eight hours1 by means of twenty     
cylindrical retorts1 attended  by the   
same number of workmen4    ,saving of   
machinery4--,when we compare the        
original cost and wear and  tear of the 
horizontal rotary retorts1 with the cost
 and deterioration  of a set of         
cylindrical1 parallelopipedal1          
ellipsoidal1 or  semi-cylindrical       
retorts of an equal power1 7that is to  
say to produce a  like quantity of gas1 

in a given time17 a difference not less 
striking  presents itself in favour of  
the horizontal retort4    ,we have      
stated already1 that cylindrical1       
ellipsoidal1 parallelopipedal1  or      
semi-cylindrical retorts1 when          
constantly kept in action1 and worked   
to the greatest advantage1 cannot be    
made to last longer than six  months4#cd
      #cd ,they are frequently rendered 
unfit for use in three months1 and    at
 some works in two months1 owing not    
less to the irregularity of the         
temperature at which they are worked1   
than to the carelessness of the         
workmen4    ,only one-third part of the 
top and bottom plates of the rotary     
retort  being exposed to the action of  
heat1 are alone liable to deterioration4
  ,it is only necessary therefore that  
these parts of the vessel be  renewed1  
while the other parts remain uninjured  
for years4 ,the new top  and bottom     
plates being rivetted to the old and    
undecayed part1 without  deranging the  

rest1 the retort is rendered as good as 
new4    ,gain in the quantity of        
gas4--,a large increase in the quantity 
of gas  obtained1 is a natural          
consequence of the mode in which the    
decomposition of coal is effected by    
means of the horizontal rotary  retort4 
,every body knows that coal1 when       
decomposed slowly1 affords a larger     
quantity of tar and ammoniacal liquor1  
but a less quantity of gas than  when   
decomposed rapidly4    ,in the former   
case1 the formation of the proximate    
products which coal  is capable of      
furnishing is effected properly2 the    
bituminous part of  the coal is         
developed under the most favourable     
circumstances4    ,but when coal1 after 
being previously deprived of moisture1  
is very  suddenly heated to a high      
temperature1 in thin strata1 and small  
portions at a time1 so that the vaporous
 products instead of becoming           
condensed1 are made to come into contact
 with a substance 7which in this  case  

is the roof of the retort17 kept        
constantly at a temperature rather      
higher than that at which gold1 silver1 
and copper melts1 7#cb1  ,wedgwood1 or  
#ebcg1 ,fahrenheit17 a very different   
arrangement of  principles takes place4 
,the greatest portion of tar which the  
coal is capable of furnishing1  instead 
of being produced in a liquid form1     
becomes then decomposed into            
carburetted hydrogen1 and olifiant gas4 
,that portion of tar which  escapes     
decomposition1 is condensed in the      
perpendicular pipe ,h1 fig4  #b1 plate  
,,ii41 or ,h1 fig4 #b1 plate ,,vii41 and
 falls back again into the  retort1     
where it is also decomposed when the    
coal upon which it falls  comes under   
the process of decomposition4    ,hence 
the quantity of tar obtained by means of
 horizontal rotary  retorts1 is very    
small2 it seldom exceeds the proportion 
mentioned page  #abc1 when the retort is
 worked to the greatest advantage4 ,this
 quantity  is considerably diminished1  

when ,newcastle coal1 broken into pieces
 of  the size of split pease is         
decomposed in strata1 not exceeding two 
inches in thickness4 ,the quantity of   
tar afforded by a chaldron of coal  then
 amounts to thirty pounds1 whilst at the
 same time the quality of  the gas is   
improved2 because coal tar furnishes    
olifiant gas1 which the  coal alone1    
when distilled by means of cylindrical  
or other shaped  cast-iron retorts of   
the usual form1 cannot produce1 or at   
least but in  a small quantity4 ,one    
gallon of coal tar yields #ae cubic feet
 of  olifiant gas1 which greatly        
increases the illuminating power of the 
carburetted hydrogen4    ,from what has 
been so far stated1 it will be          
understood why one chaldron  of         
,newcastle coal1 when decomposed by the 
new process1 may readily be  made to    
produce from #ae1jjj to #ah1jjj cubic   
feet of gas and upwards1  whereas the   
same quantity of coal1 if decomposed by 
the old method1  yields only upon an    

average #aj1jjj cubic feet of gas4#ce   
#ce ,the experiments exhibiting the     
maximum quantity of gas obtainable      
from coal1 see page #dd1 were made with 
the horizontal rotary retorts    at the 
,royal ,mint4 ,similar results have also
 been obtained at the    ,westminster   
,gas-,works4    ,in the former case1 the
 greater part of the essential oil and  
tar which  the coal would have afforded 
is decomposed1 as stated already by     
virtue  of the high temperature to which
 the vapourous tar is suddenly exposed  
in the horizontal rotary retort1 which  
is not the case when coal is  decomposed
 in the retorts of the old construction4
    ,gain in the quantity of            
coke4--,with the cylindrical or         
cast-iron  retorts of the old shapes1   
the quantity of coke obtained from a    
given  quantity of coal is upon an      
average #be per cent4 increase by       
measure  from the best kind of          
,newcastle and ,sunderland coal1 but    
taking into  account the waste incurred 

in breaking out and removing the red hot
 coke  from the retort1 which requires  
the application of rakers and crow bars1
  a considerable portion of it becomes  
reduced to dust or breeze1 and  hence no
 more than bulk for bulk of the coal    
decomposed can seldom be  depended upon 
as the ultimate saleable quantity of    
coke4#cf      #cf ,there is a vast      
difference with regard to the quality as
 well as    quantity of coke obtained   
from different kinds of coal4 ,some     
kinds of    coal produce a species of   
coke which is so friable that it will   
hardly    bear being moved from place to
 place without crumbling into dust1     
others produce coke in pieces of the    
size of small pebbles1 while a    third 
sort affords coke of a stony hardness4  
,in the new mode of carbonizing coal by 
means of the horizontal rotary  retorts1
 the increase of coke is #aej per cent4 
by measure1 so that one  chaldron of    
,newcastle coal produces two and a half 
chaldron of  coke--this is the quantity 

produced upon an average4 ,but when the 
retort  is worked at a temperature to   
produce at the rate of #ah1jjj cubic    
feet  of gas from the chaldron of coal1 
the increase of coke by measure is #age 
per cent42 in that case1 the layers of  
coal in the coal boxes must not  exceed 
two inches in thickness1 so that the    
volume of coke is in the  ratio of the  
quantity of gas produced and the        
rapidity and elevation of  temperature  
at which the decomposition of the coal  
is effected4    ,the coke being         
withdrawn from the place where it is    
formed by merely  turning the boxes     
containing it1 upside down1 all waste is
 avoided4    ,with respect1 again1 to   
the quality of the coke1 it will be     
observed  that when the coal is rapidly 
carbonized in thin layers1 and has full 
liberty to expand freely1 as in the case
 of the horizontal rotary  retort1 it   
affords a light and porous coke1 whereas
 in the cylindrical1  paralellopipedal1 
semi-cylindrical1 or ellipsoidal        

retorts1 the coke  being compressed1 the
 intense heat to which it is so long and
  superfluously exposed1 renders it     
extremely dense1 and of a stony         
hardness4    ,the latter sort of coke is
 unquestionably preferable for the      
smelter1  and all furnace operations1   
standing the blast of the bellows well4 
,but  the coke produced in the new mode 
of operating1 is better suited for  the 
great majority of domestic purposes1    
kindling more readily1 and  making a    
more cheerful fire4 ,the combustion of  
the dense1 or as it is  now called1     
cylinder coke1 can be only kept up when 
used in a common  grate1 by a strong    
draft of air1 and it is therefore not so
 well suited  for fuel for domestic     
purposes1 to make a small fire2 but the 
coke  obtained by the horizontal rotary 
retort1 readily maintains its own       
combustion1 even when in small masses2  
hence it may be used without any        
trouble1 either in the fire-place of the
 cottager1 or of the prince1 and        

accordingly it bears a higher price in  
the market4      ,directions to workmen1
 with regard to the management of       
,horizontal  ,rotary ,retorts4    ,the  
circumstance most essential to the      
economical application of the           
horizontal rotary retort1 is1 as has    
been repeatedly stated1 that the  coal  
shall be spread in thin layers in the   
boxes of the retort1 not  exceeding from
 two to four inches in thickness2 and it
 may be laid down  as a general rule1   
that the thinner the layers1 and the    
higher the  temperature1 the greater    
will be the proportion of gas1 the      
greater the  bulk of coke1 and the      
smaller the quantity of tar4    ,the    
coal before it is submitted to the      
distillatory process1 should be  as dry 
as possible1 and the more it is         
comminuted the better4 ,the very  refuse
 of the coal called slack1 provided it  
is perfectly free from  foreign matter1 
answers best4 ,it should also be spread 
in the trays1 in  even layers4    ,when 

the retort is in a good working state1  
the temperature should be  kept up by   
the application of small quantities of  
fuel at a time4 ,a  prodigious saving of
 fuel may be effected by attending the  
fire  properly1 and it is this which    
distinguishes a careful stoker from a   
bungler4 ,for in the working of this    
retort particularly1 it is a  wasteful  
process to clog up the fire-place with a
 large quantity of fuel  injudiciously  
applied4 ,the difference in this        
respect1 with regard to  the economy of 
fuel is so great1 that an expert stoker 
will work the  retort with one-third    
less of fuel and half the labour that   
would be  employed by a negligent       
workman4    ,the quantity of gas        
produced from a chaldron of coal may be 
ascertained  by the gas metre1 or by the
 gas holder1 if the outlet valve of the 
latter be shut during the distillatory  
process4    ,the heat at the same time  
employed for working the retort1 will be
 best  defined for the stoker's guide1  

by copying carefully on paper the red   
tint of the retort1 as seen through the 
sight hole1 made for that  purpose in   
the brick-work directly over the        
fire-place4    ,the first six feet of   
the perpendicular pipe ,h1 fig4 #a1     
plate ,,ii41 which  conveys the         
distillatory products from the retort1  
should be well  cleaned out once a      
month1 the bonnet at the bended part of 
the pipe ,h1  fig4 #a1 is provided for  
that purpose1 as already stated1 page   
#aai4    ,when the retort remains       
uncharged1 the fire must be kept low in 
order to  prevent its getting beyond the
 usual temperature1 and the arms and    
moveable axis should be turned          
occasionally1 and the door kept close4  
,the fire tiles which cover the flues   
under the retort should be examined     
about once a fortnight1 and if a tile is
 melted or broken1 it must be  replaced 
by a new one1 because the preservation  
of the retort greatly  depends upon this
 precaution4    ,all the parts of the   

arms composing the moveable disc within 
the retort1  may be taken out of the    
door of the retort1 if they should      
require a  repair1 first taking off the 
cap from the perpendicular pipe ,e1 fig4
 #a1  plate ,,ii41 surrounding the shaft
 of the retort1 then the centre piece1  
or rose centre1 ,f1 fig4 #b1 plate      
,,ii41 the shaft ,d1 fig4 #b1 plate     
,,iii41  may be drawn up through the    
pipe which surrounds it4    ,when the   
retort requires cleaning1 which should  
be done once every six  or eight months1
 a screw may be attached to the upper   
extremity of the  shaft ,d1 which passes
 through the retort2 by this means1 the 
arms and  rose centre within the retort 
can easily be raised1 to leave the      
bottom  of the retort quite clear1 in   
order that the lumps of coke1 that may  
be  scattered about1 may be easily      
removed4 ,and if an incrustation of coke
  should happen to be attached to the   
bottom of the retort1 it may be  readily
 detached by a crow bar1 or other       

suitable instrument4    ,the trays or   
coal boxes1 fig4 #ab1 plate ,,ii41 may  
be made by the stoker1  of sheet iron1  
7called in commerce ,no4 #af17 framed   
upon a wooden mould  made for the       
purpose4    ,the temperature best suited
 for the decomposition of coal by means 
of  the horizontal rotary retort        
depends1 as has been already stated in  
the  case of cylindrical cast-iron      
retorts1 altogether on the price of     
coal1  and the price which can be       
obtained for the coke4    ,in all places
 where the average price of coal1 equal 
in quality to  7,bewick and ,craister's 
,walls ,end7 ,newcastle coal1 or any    
other species  of coal1 capable of      
producing from fifteen to eighteen      
thousand feet of  gas from one chaldron1
 is not less than  #b4 #hs4 the chaldron
 7#bg ,cwt47  or upwards1 and where coke
 can be sold at the average price of 4  
#a the  chaldron1 the horizontal rotary 
retort should be worked at such a       
temperature1 that when viewed through   

the sight hole1 it shall appear of  a   
bright cherry redness1 and at which it  
produces from #ae1jjj to #af1jjj  cubic 
feet of gas1 from a chaldron of coal4   
,but in all other places where coal of  
the same quality to 7,bewick and        
,craister's ,walls ,end7 ,newcastle     
coal1 may be purchased at 4 #a #hs4 the 
chaldron1 or at a less price1 it will be
 more advantageous to the  manufacturer1
 to work the horizontal rotary retort1  
at a lower  temperature1 so as to       
produce only at the rate of thirteen or 
fourteen  thousand cubic feet of gas    
from the chaldron of coal4 ,in the      
latter case  the manufacturer expends   
coal in order to save his retort1       
whereas in  the former case he          
economizes the fuel1 as productive of a 
gain more  than commensurate for the    
waste of the retort4    ,when the supply
 of gas required1 happens at any time to
 be less than the  retort when in action
 is capable of furnishing1 the fire must
 then be  kept low1 but the retort      

should never be suffered to acquire a   
lower  temperature1 than that of a dull 
red heat visible by day-light4          
,,part ,,viii4      ,purifying          
,apparatus1 or ,lime ,machine4    ,coal 
gas1 even as obtained from the best     
species of coal1 must be  rendered pure 
before it is fit for the purpose of     
illumination4 ,the gas  in its crude    
state always contains a portion of      
sulphuretted hydrogen  and carbonic     
acid2 and when burnt1 although its      
illuminating power is  greater in an    
impure than in a pure state1 it produces
 an oppressive and  suffocating odour1  
which is speedily perceptible in        
confined places4 ,the  gaseous product  
evolved during its combustion1 blackens 
paint and  tarnishes metallic bodies2 an
 impure gas besides strongly acts upon  
the  copper branch pipes through which  
it is conveyed4    ,to obviate these    
defects the sulphuretted hydrogen and   
carbonic acid  which are the cause of   
them must be removed1 and to effect     

this1 no  method more economical and    
efficacious1 has as yet been discovered1
 than  to bring the gas confined under a
 pressure equal to a column of water1   
not less than eight or ten inches in    
height1 into contact with  quick-lime1  
diffused through water4 ,other means    
have been tried1 but all  of them have  
failed to be sufficiently efficacious or
 economical on a  large scale4          
,lime ,machine originally employed for  
the ,purification of ,coal ,gas4    ,in 
the lime-machine1 until lately in use1  
the gas was made to pass in  the        
apparatus1 through passages which could 
not be guarded from being  stopped up in
 the course of time by the concretion of
 a quantity of  carbonate and           
hydro-sulphuret of lime1 formed during  
the purification of  the gas1 so that   
when the stoppage occurred1 a prodigious
 pressure was  produced in the machine1 
in consequence of which1 it was either  
found  impossible to keep the           
distillatory apparatus air-tight1 or if 

this was  accomplished1 a great part of 
the gas was forced through the purifying
  apparatus1 without coming in contact  
with the lime1 by driving the  column of
 mixture of lime and water before it1   
and of course without  being rendered   
fit for use1 previous to its passing    
into the gas  reservoir4 ,this effect   
was unavoidable without the precaution  
of  employing a very dilute mixture of  
quick-lime and water4    ,numerous      
instances have also occurred where from 
the increased pressure  which the gas   
exerted in the lime apparatus1 the tar  
from the hydraulic  main was driven up  
with a prodigious force through the dip 
pipe1 ,p1 fig4  #b1 plate ,,iv41 into   
the retort when the retort was opened1  
where it took  fire to the imminent     
danger of the whole establishment4      
,the apparatus originally employed was  
composed of a large vessel closed  on   
all sides to receive the gas2 within    
this was a smaller vessel or  lime      
trough open at top containing the       

quick-lime and water2 and there  was    
also a third vessel1 or inverted trough 
into which the gas was  received4       
,this inverted trough was open at       
bottom1 and the edge of the open part   
was immersed beneath the surface of the 
mixture of lime and water  contained in 
the lime-trough1 so that the gas which  
was introduced in  the last-mentioned   
inverted trough could not escape        
therefrom1 except  rising up through the
 lime and water4 ,to facilitate this1   
holes or  openings were made in the     
inverted trough near the bottom edge    
thereof1  and beneath the surface of the
 purifying mixture1 so that the bubbles 
of  gas were obliged to rise up through 
these openings4 ,from this  construction
 of the machine the apertures through   
which the gas had to  pass1 were        
extremely liable to become stopped up1  
and dangerous  consequences ensued4     
,in order to remedy in some measure the 
evil1 a plan was adopted by ,mr4        
,malam1 for making the gas to pass in   

thin strata underneath a series of      
shelves1 placed horizontally in the     
machine so as to expose the gas in  as  
large a surface as possible to the      
contact of the lime and water1 and      
employing the purifying mixture at the  
same time in a more dilute  state3--this
 arrangement is as follows4    ,fig4 #d2
 plate ,v41 represents a vertical       
section of the machine2 it is  made of  
cast-iron plates1 rendered air-tight by 
screws1 bolts1 and iron  cement4 ,it    
consists of three separate chambers1 a1 
a1 a1 destined  to contain the mixture  
of quick-lime and water4 ,at the under  
side of  each chamber1 is bolted a      
cylinder1 h1 h1 h1 the lower extremity  
of which is furnished with a large      
flanch1 extending nearly to within  the 
whole inner diameter of the machine4    
,from the bottom of each of the         
chambers1 a1 a1 a1 proceeds a pipe      
curved upwards1 and communicating with a
 circular vessel1 ,c1 ,c1 ,c1 which     
serve for the purpose of charging the   

chambers1 a1 a1 a1 with the  mixture of 
quick-lime and water1 and regulating the
 level of the fluid  within the         
chambers4 ,the curved pipe likewise     
prevents the escape of the  gas when the
 contents of the chambers a1 a1 a1 are  
discharged4    ,the vessels1 ,c1 ,c1 ,c1
 are provided with a waste pipe and     
stop-cock1 as  shown in the sketch1 for 
discharging the contents of one chamber 
into  the chamber placed below it1 and  
lastly into the reservoir e4    b b1 are
 pipes which convey the gas into the    
chambers1 one extremity  of each pipe   
communicates with the cylinders h1 h1 h1
 and the  other with the chamber below  
it1 and the lower pipe communicates with
  the valve ,m1 so that by this means a 
communication is formed from the  lower 
cylinder h1 to the middle cylinder h1   
and from the middle to  the uppermost   
cylinder4 ,k1 is the exit pipe which    
conveys the purified  gas from the      
uppermost chamber into the reservoir    
destined to receive  it4 ,through the   

centre of the machine passes a          
wrought-iron shaft1  furnished with     
agitators or arms1 to stir up the       
mixture of quick-lime  and water4 ,the  
arms are not immediately connected with 
the shaft1 but  proceed from cast-iron  
hydraulic cups1 of the usual            
construction1 by  this means the escape 
of the gas is prevented1 nor can the    
fluid pass  from one chamber into       
another4 ,the axis is put in motion1 by 
wheel-work  as shown in the design e1   
the handle for turning the shaft4    g1 
is a receiver to collect the condensible
 products4 ,the contents of  this vessel
 may be discharged by a hand pump being 
attached to the upper  extremity of the 
pipe f1 after the cap with which it is  
closed is  removed4    ,the operation of
 this lime machine is obvious4 ,the gas 
first passes into  the lowermost chamber
 of the cylinder h1 where it comes in   
contact  with the purifying mixture and 
passes through the fluid to the top of  
the same chamber1 and thence through the

 pipe b1 into the cylinder  above it    
which communicates with the lower       
chamber1 where it is acted on  again by 
the lime and water1 and bubbles up      
through the fluid to the top  of the    
chamber4 ,from this compartment the gas 
passes into the third  cylinder1 where  
it bubbles up and passes through the    
lime and water2 and  lastly it makes its
 exit through the pipe ,k1 into the     
gasholder or  vessel destined to receive
 it4    ,when the mixture of quick-lime 
and water in the compartments a1 a1  a1 
of the machine1 requires to be renewed1 
it is let off by the  stop-cock at the  
bottom of the lowermost vessel into the 
reservoir e4  ,the fluid contained in   
the upper chamber may be discharged into
 the  chamber below it1 and so on with  
the chambers below it1 care being taken 
to close the stop-cock of the lower     
vessel4 ,the machine may be recharged   
at the uppermost chamber with the       
purifying mixture4 ,fig4 #e1 exhibits   
the plan of the machine4 b1 b1 b1 the   

tubes connecting the  chambers4 ,b1 the 
flanch of the cylinder h4    ,this      
machine has in part remedied the        
inconveniences stated pages #ada1  #adb1
 but the increase in the quantity of the
 purifying materials which  the         
apparatus requires1 is of itself        
productive of most serious              
disadvantages4    ,the greater          
accumulation of waste lime which such a 
practice occasions1  renders it         
necessary that capacious reservoirs and 
sewers should be  constructed to receive
 and carry off the refuse materials1 and
 where an  outlet by such means cannot  
be obtained1 the carting away the       
increased  quantities of waste matter   
adds greatly to the cost of the gas4    
,if attempts are made to convey the     
waste substances into the common  sewers
 or drains of the neighbourhood1 the    
proprietors of gas works are  exposed to
 indictments for a nuisance at the suit 
of the inhabitants1  and when the near  
proximity of any river or lake induces  

an attempt to  convey the waste         
materials thither1 the most serious     
injury may be done  to the water1 which 
becoming impregnated with hydrosulphuret
 of lime is  rendered unfit not only for
 domestic but for many manufacturing    
purposes4 ,the latter evil indeed is one
 which operates also in a greater  or   
lesser degree1 even when the ftid refuse
 or hydrosulphuret is  discharged into  
the common sewers1 all of which         
ultimately empty  themselves into some  
water course1 rivulet or lake4 ,i would 
here beg to  suggest1 that considering  
how rapidly the new mode of procuring   
light is  extending throughout          
,britain1#cg and how much the waters of 
the country  are liable to be           
contaminated1 from discharging into them
 the noxious  refuse from the process of
 purifying coal gas1 so as to be        
rendered  proportionably unfit for the  
various purposes of domestic and        
manufacturing economy1 it is well       
deserving the attention of the          

legislature1 whether such contamination 
ought not to be guarded against  by     
prohibiting enactments4      #cg ,the   
,towns of ,edinburgh1 ,glasgow1         
,liverpool1 ,bristol1 ,bath1            
,cheltenham1 ,birmingham1 ,leeds1       
,manchester1 ,exeter1 ,macclesfield1    
,kidderminster1 ,preston1 ,waterford1   
,rochester1 ,chatham and several        
others1 have been lighted with gas      
within these few years4    ,it appears  
to me that it would be a wise exertion  
of authority1 to  insert in every act of
 ,parliament granted for incorporating  
,gas-light  ,companies1 a clause        
prohibiting the proprietors from ever   
conveying the  waste material1 or any   
other produce from the manufacture of   
coal gas1  either directly or indirectly
 into the common sewers1 drains or water
  courses1 or into rivers and lakes     
adjacent4 ,the salubrity of the water   
we use is of as much consequence to us1 
as any superior excellence or  saving of
 cost in our light can possibly be1 and 

we ought to take care  that in profiting
 by an improvement which science and art
 have  discovered1 we do not            
unnecessarily depreciate one of those   
primary  blessings we owe to the bounty 
of nature4      ,lime ,machine lately   
adopted4    ,in the improved purifying  
apparatus#ch lately brought into use1 of
  which we shall now give an account1 a 
shaft or axis furnished with teeth  or  
claws1 is applied within the interior of
 the vessel1 and made to act  in such a 
manner as to scrape out the openings or 
slits through which  the gas has to pass
 every time the axis is moved round1 and
 by which  regular clearance all chance 
of stoppage is avoided without any      
augmentation of the purifying mixture4  
#ch ,this machine has been adopted at   
the gas works at ,chester1              
,birmingham1 ,kidderminster1 ,bristol1  
and in many other provincial ,gas       
,establishments4    ,the lime trough is 
also made moveable on a centre or axis1 
in such a  manner that it may readily be

 inverted by a lever from the outside1  
for  the purpose of emptying its        
contents into the bottom of an exterior 
vessel1 from which the waste materials  
may be discharged at pleasure4    ,with 
this machine we are farther enabled to  
employ the purifying mixture  in a      
semi-fluid state1 and consequently in a 
much less bulk2 and after  having       
suffered it to remain in the reservoir  
destined to receive it1  the waste      
substance speedily acquires such a      
degree of solidity that it  may be dug  
out with a spade and carted away in a   
small compass4 ,the  safety of the      
apparatus is therefore insured and the  
construction of  expensive drains and   
sewers is rendered unnecessary4 ,the    
following  description will render the  
construction of the improved apparatus  
obvious4    ,a1 ,a1 fig4 #b1 plate      
,,ii41 is a rectangular four-sided      
prism1 made of  cast-iron plates1       
screwed together air-tight with bolts   
and cement4 ,the  base of the prism     

terminates in a rectangular four-sided  
pyramid placed  with its apex downwards4
 ,it is surrounded by an iron stage1    
supported  upon pillars1 as shown in the
 design4    ,within this vessel1 which  
in fact composes only the outer case of 
the  apparatus1 is contained an oblong  
trough ,b1 fig4 #b1 plate ,,ii41 7it is 
shown in the design as if broken down71 
moveable upon an horizontal  axis1 fixed
 to one of its longest sides1 so that by
 means of the wheel  ,c1 or lever       
communicating with the axis1 and applied
 on the outside of  the machine1 the    
trough ,b1 may be inverted1 and its     
contents discharged  into the exterior  
case1 or lower part ,a1 ,a1 of the      
machine4 ,the part ,b1  of the machine  
is called the lime trough1 because it is
 destined to  contain the quick-lime and
 water1 by means of which the crude coal
 gas  is purified4 ,within this trough  
,b1 is inverted an oblong rectangular   
box  ,d1 closed at top and open at      
bottom1 called the air-box1 because it  

receives the gas to be purified4    ,in 
each of the longest sides of the box ,d1
 are perpendicular openings or  slits   
7as shown in the design7 exactly        
opposite to each other4 ,through  the   
whole length of this box ,d1 passes a   
horizontal axis furnished with  as many 
teeth or claws as there are upright     
openings1 through each side  of the box4
 ,these claws extend a little way       
through the openings so that  when the  
axis1 which passes through a stuffing   
box1 is made to revolve  by means of the
 handle ,x1 the ends of the claws pass  
through the  openings and scrape them   
out every time the axis is turned4 ,the 
claws  operate first on the openings of 
one side of the box and then on those   
on the opposite side4 ,they pass quite  
through and therefore keep them  clear2 
those parts of the claws which enter    
into the openings are narrow  in the    
direction of their motion1 and that part
 of each claw which is  nearest to the  
centre1 is broad and flat1 hence they   

act as paddles or  rowers whilst they   
are in motion1 to stir up the quick-lime
 and water4    ,fig4 #aj1 plate ,,iii41 
represents a transverse section of this 
part of the  apparatus4 ,b1 ,b1 is the  
lime trough2 ,d1 the air box inverted   
into the  lime trough2 the dotted circle
 shows the sweep of the claws when the  
shaft is put in motion4 ,the darts show 
the course of the gas4    ,fig4 #aj1    
plate ,,vi41 represents a plan of the   
machine4 ,g1 shows the  inverted        
air-trough with its axis1 and the claws 
or teeth fixed upon the  axis4 ,h1 is   
the lime trough4 ,a1 the outer case of  
the machine2 ,r1 ,r1  the axis1 to which
 is affixed the wheel or lever1 for     
inverting the  trough ,h4 ,l1 the axis  
and handle to give motion to the shaft  
upon which  the claws are fixed1 for    
stirring up the contents of the lime    
trough4    ,the inverted air-box ,d1    
fig4 #b1 plate ,,ii41 is supported      
within the outer  case of the machine   
,a1 ,a1 fig4 #b1 plate ,,ii41 by cross  

bars1 and the axis  is put in motion by 
the handle ,x1 on the outside of the    
machine4 ,it is  rendered air-tight by a
 stuffing box1 and is provided with     
wheel-work1  as shewn in the design1    
fig4 #b1 plate ,,ii41 to communicate the
 motion to  the axis4    ,the gas is    
brought into the air box by the pipe ,n1
 fig4 #c1 which  proceeds from the tar  
vessel1 fig4 #c1 plate ,,ii4 ,the gas   
cannot escape  out of the machine       
without displacing the column of fluid  
in the lime  trough1 in order to make   
its way through the openings or upright 
slits  in the side of the air box ,d1   
and thus bubbling up through the mixture
  of quick-lime and water1 the depth of 
which is one foot4 ,the  sulphuretted   
hydrogen and carbonic acid being thus   
made to combine with  the lime1 the     
carburetted hydrogen is left more or    
less pure1 it is  conveyed into the gas 
metre1 by the pipe ,v1 where it is to be
 measured1  and from thence by the pipe 
,w1 fig4 #d1 into the gas-holder4       

,when the purifying mixture is to be    
removed1 the workman unbolts the  wheel 
,c1 fig4 #b1 and turns it half way      
round2 7if the emptying of the  lime    
trough requires more power than can     
conveniently be applied by  means of the
 wheel1 the axis of the trough may be   
worked with a tooth  and pinion1 a small
 wheel being attached to the axis of the
 pinion as a  perpetual handle27 this   
motion inverts the lime trough ,b1 and  
its  contents become discharged into the
 outer case forming the inverted        
pyramid of the apparatus1 whence the    
waste materials may be conveyed  into   
the reservoir or pit ,q1 by drawing open
 the sliding valve o1 fig4  #b1 plate   
,,ii41 or o1 fig4 #c1 plate ,,vii41     
added for that purpose to the           
discharging pipe ,p1 fig4 #b1 plate     
,,ii41 or p1 fig4 #c1 plate ,,vii4 ,to  
prevent the air entering into the       
machine when the waste lime is          
discharged1 the lower extremity of the  
outlet pipe ,p1 dips into the  basin ,q1

 fig4 #b1 plate ,,ii41 which always     
contains a portion of the waste  fluid  
and thus seals the extremity of the pipe
 ,p4    ,one side of the lime-machine is
 provided with two large lenses1 to     
admit light into the interior of the    
apparatus1 so that by means of an       
eye-glass fixed in a proper place1 the  
workman is enabled to see into  the     
interior of the apparatus4 ,and when the
 machine requires to be  cleaned out1   
the manhole as it is called1 is opened  
for the workmen to  enter into the      
apparatus to remove any solid           
incrustation of carbonate  of lime1 or  
hydrosulphuret of lime that may happen  
to be formed in the  lime trough1 or any
 other part of the apparatus4    ,the   
wheel ,c1 is loaded with a              
counter-weight1 to balance the weight of
  the lime trough4 ,to bring the lime   
trough again into a proper position1  to
 be re-charged with a fresh portion of  
the purifying mixture1 the  workman     
turns the wheel ,c half round1 the      

contrary way to that which  caused the  
trough to be turned topside-down1 and   
the trough may then be  re-filled with a
 fresh portion of lime and water from   
the reservoir ,r1  fig4 #b1 plate ,,ii41
 7or ,r1 fig4 #c1 plate ,,vii417        
containing the mixture  ready prepared4 
,y1 is a pipe to bring water from a     
cistern into the lime  reservoir ,r4    
,the prepared lime which is to supply   
the machine is put  into the vessel ,r1 
and a sufficiency of water being mixed  
with it1 the  mixture is stirred up to  
the consistence of a semi-fluid mass4   
,t1 shows the pipe furnished with a     
sliding valve ,s1 for conveying the     
purifying mixture of quicklime and water
 into the lime trough from the          
reservoir ,r1 which is furnished with an
 agitator to stir up its  contents4     
,to give motion to the shaft for        
stirring up the contents of the lime    
trough ,d1 the inventor of this machine 
7,mr4 ,clegg17 has happily applied  the 
gas1 to act as a power for that purpose4

 ,this operation will be  explained     
hereafter in describing the gas metre4  
,the pipe ,n1 which conveys away the    
purified gas1 proceeds from an          
hydraulic valve1 to cut off the         
communication between the gas holder and
  the lime machine1 if occasion should  
require it1 and to prevent the gas  from
 passing back from the gas holder into  
the lime machine4    ,it consists of a  
box containing water into which dips a  
small pipe1 by  means of which the gas  
passes out of the lime machine1 and from
 thence  into the pipe ,v1 communicating
 with the gas metre4 ,the box is        
furnished  with a tube curved upwards to
 discharge the water when it accumulates
  above the required height1 and to     
prevent any quantity being thrown out   
of the hydraulic valve1 by the          
concussion of the fluid in the lime     
trough4    ,one cubic foot capacity of  
the lime trough is sufficient to purify 
#ajjj  cubic feet of gas obtained from  
,newcastle coal in twenty-four hours4   

,test ,apparatus1 for certifying the    
purity of coal gas1 and the proper      
manner of working the ,lime ,machine4   
,the proper purification of the gas     
being a matter of essential  importance1
 as already illustrated page #adj1 it   
becomes of great  consequence to have   
some ready means of ascertaining whether
 the workman  does his duty in this     
respect1 by keeping the lime trough ,d1 
fig4 #b1  plate ,,ii41 properly charged 
with the requisite quantity of lime and 
water necessary for the purification of 
the gas4    ,for this purpose an        
apparatus has been adapted by ,mr4      
,clegg to the lime  machine1 which      
serves not only to indicate the quantity
 of fluid  contained in the machine when
 gas is manufactured1 but which also    
enables the workmen to appreciate the   
quantity of quick-lime necessary  for   
the purification of the gas1 and to     
ascertain its purity4 ,the  apparatus   
consists of a closed cup ,c1 fig4 #bc1  
plate ,,iv41 partly filled  with any    

coloured liquid4 ,into this cup is      
cemented1 air-tight1 a  straight glass  
tube a1 about #b feet long and a  of an 
inch in  the bore2 the lower extremity  
of the tube nearly touches the bottom of
  the cup1 and is therefore sealed by   
the fluid4 d1 d1 is a small  copper     
tube1 which forms a communication       
between the air confined above  the     
surface of the fluid in the guage cup   
,c1 and the gas which is  proceeding    
into the lime-trough4    ,the           
communication may be established at any 
part of the pipe which  conveys the gas 
into the lime machine4 ,when the        
connection is made1 the  fluid in the   
guage cup ,c1 will be driven up into the
 perpendicular  measuring tube a1 by the
 pressure of the gas1 to an altitude    
equal to  a column of liquid contained  
in the lime-trough4 ,it is essential    
that  the tube a1 be at least #b feet in
 height1 if the depth of the            
lime-trough is one foot1 for without    
this precaution1 the fluid will  rise   

out of the tube in consequence of the   
oscillation which it suffers4  ,by this 
means the overseer of the works will be 
enabled1 by mere  inspection1 to know   
whether the workmen have charged the    
lime trough  with the mixture of        
quick-lime and water to the requisite   
height1 which  should never be less than
 from ten to fifteen inches4 ,because   
the  abstraction of the sulphuretted    
hydrogen and carbonic acid gas1 from the
  carburetted hydrogen with which it is 
combined1 is greatly facilitated  by    
pressure1 and there is no inconvenience 
whatever in operating under a  pressure 
of a column of fluid of even double the 
height that has been  stated1 provided  
the apparatus is properly constructed4  
,from experiments  made on this subject1
 ,i am justified in stating that one    
half of the  quantity of quick-lime that
 is required for the purification of    
coal gas  in the ordinary way1 is       
sufficient1 if the column of the liquid 
opposed  to the gas is raised to twenty 

inches high1 nor is the evolution of the
  gas in any degree retarded under such 
a pressure4    ,the curved tube d d1    
which is cemented air-tight into the    
gauge cup  c1 has a free communication  
with the gas in the guage cup c4 ,it    
serves to enable the workmen to form    
some notion of the chemical             
constitution of the crude gas1 before it
 passes into the lime machine4  ,for if 
the stop cock e of the tube be opened1  
and the descending leg  a of the bended 
tube d be immersed in a glass containing
 a solution  of super acetate of lead1  
some notion may be formed by a little   
practice  of the quantity of lime       
requisite for the purification of the   
gas1 from  the quantity of 7black       
precipitate7 hydrosulphuret of lead     
produced4 ,two  per cent of quick-lime  
to the coal employed 7if ,newcastle     
coal7 is  usually sufficient for the    
complete abstraction of all the         
sulphuretted  hydrogen and carbonic     
acid1 contained in the crude gas1       

provided the  operation be carried on   
under a pressure of not less than a     
column of  water twelve inches in       
height4    ,the test tube f1 properly so
 called1 may be adapted to any part of  
the  pipe which conveys the purified gas
 to its place of destination4 ,it       
serves to ascertain the purity of the   
gas1 after it has been acted on by      
quick-lime1 by suffering the gas to pass
 from the tube into a solution  of super
 acetate of lead1 which speedily becomes
 discoloured1 if the  gas contains      
sulphuretted hydrogen4 ,the presence of 
carbonic acid is  rendered obvious1 by a
 white precipitate being produced when  
the gas is  made to pass through barytic
 water4 ,the precipitate1 which is      
carbonate  of barytes1 effervesces with 
acids4    ,it must be obvious that the  
apparatus which we have now been        
describing  does not require to be      
placed in the immediate vicinity of the 
gas light  machinery4 ,it may be        
arranged in the counting-house of the   

overseer1  who1 by mere inspection1 can 
then at all times detect the slightest  
irregularity or insufficiency in the    
process thus given to the gas light     
manufacture1 a degree of scientific     
controul of which few arts can  boast4  
,the following method has been found    
economical and convenient1 for          
preserving quick-lime in a ready state1 
fit for the purification of coal  gas4  
,take the lime as soon as possible after
 it is burnt2 put it into a pit  eight  
or ten feet long1 five or six wide1 and 
five or six deep1  constructed of       
brick-work and level with the ground4   
,by this pit set a  wooden trough about 
six feet long1 three feet broad1 and two
 feet deep4  ,the trough should have at 
one end a hole about six inches square1 
covered with an iron grating1 the bars  
of which are a quarter of an  inch      
distant4 ,let this grating be provided  
with a slider1 which can  occasionally  
be drawn up to uncover1 or pushed down  
to cover1 the  grating4 ,put three or   

four bushels of lime at a time into the 
trough2  throw water on it1 and mix it  
up into a thick fluid mass with a hoe   
perforated with holes4 ,when there is a 
good quantity of liquid1 draw up  the   
slider and let the slacked lime run into
 the pit4 ,throw more water  on the     
remaining unslacked lime1 and lastly    
reject those pieces which  will not     
slack4 ,the trough should have a small  
inclination and project  over the pit4  
,after the lime thus slacked has been   
five or six hours in the pit1 it  will  
take the consistence of a stiff paste1  
which it retains for years4  ,it should 
then be kept covered to keep it clean   
and to exclude the free  contact of the 
air4 ,for those who use larger          
quantities of lime1 several  pits should
 be constructed in preference to one    
larger reservoir4 ,when  the lime is    
wanted for use it may be dug out with a 
spade1 and readily  diluted with a      
sufficient quantity of water4    ,the   
quick-lime thus prepared forms a perfect

 homogeneous mixture4 ,the  practice of 
throwing lime simply slackened into the 
lime cistern is a  wasteful and slovenly
 process1 as will becomes obvious on    
examining the  waste hydrosulphuret of  
lime discharged from the machine1 which 
will be  found to abound with lime in a 
concrete form1 unacted on by the        
substances with which it was intended to
 combine4          ,,part ,,ix4         
,gas ,holder4    ,the name of gas       
holder1 or1 as it is improperly called1 
gasometer1 is  given to the vessel      
employed for collecting the gas and     
storing it up  for use4 ,in the         
principle and construction of this part 
of the gas light  machinery1 peculiarly 
valuable improvements have of late been 
made4 ,they  have contributed to lessen 
the expence of the apparatus so much1   
that a  reservoir for storing up any    
quantity of gas1 may now be furnished   
for  nearly one half the sum which such 
a vessel cost as originally             
constructed4    ,in the infancy of the  

art of lighting with coal gas1 the      
reservoir was  encumbered with a heavy  
appendage of chains1 wheel-work and     
balance  weights1 and from the          
construction of the machine1 it was     
necessary to  guard it from the impulse 
of the wind1 the action of which on the 
gas  holder1 would have rendered the    
lights which the machine supplied with  
gas1 unsteady4    ,hence it was         
necessary to inclose the gas holder in a
 building1 called  the gasometer house1 
which formed one of the largest items of
  expenditure which the proprietor of a 
gas light establishment was called  upon
 to defray4    ,now1 however1 the whole 
of these expensive appendages is        
dispensed with1  nor is the gasometer   
house to contain the gas holder any     
longer  necessary1 and the machine as   
now constructed may be fixed in the open
  air4      ,gas ,holder as originally  
employed4    ,the gas holder1 of the    
original construction1 consists of two  
principal  parts2 first1 of a cistern or

 reservoir of water1 usually constructed
 of  masonry1 or of cast-iron plates1   
bolted and screwed together2 and        
secondly1 of an air-tight vessel which  
is closed at top and open at  bottom1   
inverted with its open end downwards    
into the cistern of water4  ,this vessel
 is always made of sheet-iron plates    
rivetted together  air-tight1 and was   
suspended by a chain or chains1 passing 
over wheels1  supported by a frame work4
    ,if the common air be allowed to    
escape from the inner vessel1 when its  
open end is under the edge of the water 
in the outer cistern1 it will  freely   
descend1 and water will occupy the place
 of the air2 but if the  avenue of the  
escape be stopped1 and air be made to   
pass through the  water1 the suspended  
inverted vessel will rise to make room  
for the air4  ,and1 again1 if the       
suspended vessel be counterpoised by a  
weight1 so as  to allow it to be a      
little heavier than the quantity of     
water which it  displaces1 it will      

descend1 if1 the entering gas be        
withdrawn through an  outlet made in the
 vessel to permit the gas to escape4    
,but if the outlet  be stopped1 and air 
again be admitted under the vessel1 it  
will rise  again4 ,the apparatus1       
therefore1 is not only a reservoir for  
storing up  the gas introduced into it1 
but serves to expel the gas which it    
contains1 when required1 into the pipes 
and mains connected with this  machine4 
,according to this construction of the  
apparatus the interior inverted  vessel 
forms strictly what is termed the gas   
holder4 ,it is suspended as  already    
stated in the outer cistern1 by a chain 
or chains1 passing over  pullies1       
supported by blocks and frame work1 and 
to the chain there is  affixed a        
counterpoise balance1 of such a relative
 weight1 as to allow  the gas holder a  
slow descent into the water1 in order to
 propel the gas  into the mains or      
vessel destined to receive it1 with a   
very small and  uniform weight4    ,it  

will be obvious1 that when a gas holder 
of this construction becomes  immersed  
in the water1 it loses as much of its   
weight as is equal to the  bulk of water
 which it displaces1 and hence to render
 its descent  uniform1 and to preserve  
the gas within1 of an invariable        
density1 at  any degree of immersion1 a 
greater counterpoise is required as the 
gas  holder rises out of the water4     
,among various methods which have been  
adopted to attain this object1 the  ends
 of the chains by which the gas holder  
is suspended1 have been  fastened in    
separate grooves1 in the edge of a large
 wheel or pulley1 of  such a diameter1  
that the gas holder rises to its full   
height1 before  the wheel makes one     
revolution4    ,in another groove in the
 edge of the same wheel1 was fixed the  
end of  another chain1 to which a       
balance weight was suspended4 ,this     
weight was  made nearly equal to the    
weight of the gas holder4 ,to equalize  
the  density of the gas within the gas  

holder1 at any degree of immersion of   
the vessel1 the weight chain was made to
 pass over a wheel1 furnished  with a   
spiral groove1 so as to make the radii  
of the wheel1 change  reciprocally with 
the relative weight of the gas holder1  
and  consequently to render the pressure
 of the gas holder constant and         
uniform4    ,another and more elegant   
method of obtaining an uniform          
elasticity of  the gas within the gas   
holder1 and which has been more         
generally  adopted1 consists in passing 
the chain or chains by which the gas    
holder  is suspended over a pully or    
wheels1 and making the weight of that   
portion of the chain1 which is equal to 
the depth of the gas holder1 or  that   
part of it which becomes immersed into  
the water1 equal to one  half of the    
weight of the specific gravity of the   
gas holder4    ,it is obvious that      
before the purified gas can be admitted 
into the gas  holder1 the vessel must be
 allowed to descend to the bottom of the

  exterior cistern1 in order to get rid 
of the common air which it  contains4   
,this may be effected rapidly by opening
 the man hole at the  top of the gas    
holder1 to cause the vessel to descend  
completely into  the outer cistern      
filled with water4 ,the man hole is then
 screwed up  again air-tight1 and the   
machine is ready to receive the gas4 ,it
 is  obvious that the operation of      
opening the man hole for letting out the
  common air1 requires only to be done  
once prior to the commencing of the     
working of the apparatus4      ,gas     
,holder with ,governor1 or ,regulating  
,gauge1 lately brought into  use4    ,it
 must be obvious that the gas holder1 of
 which a description has been  given in 
the preceding page1 requires a machinery
 at once ponderous and  very delicate1  
qualities not easily reconciled in the  
construction of  such a machine4 ,it is 
necessary that the specific gravity     
apparatus1 or  regulating chain1 wheel  
work and balance weight1 should be      

constructed  so correctly as never to   
suffer the gas within the vessel1 to    
alter its  elasticity4 ,the machinery   
requires an expensive framing for its   
support1  and independently of this1 the
 gas holder must be inclosed in a       
building1 in order to protect it from   
the impulse of the wind1 the  action of 
which would render the lights supplied  
from the apparatus  unsteady1 as already
 stated4 ,the expensive and cumbersome  
specific  gravity apparatus has been    
wholly superseded by an ingenious       
contrivance  called the regulator or    
governor4 ,the action of this machine1  
for which  we are indebted to ,mr4      
,clegg1 is1 that it regulates the       
density of the  gas prior to its        
entering into the mains1 to any required
 degree1  whatever its density may be in
 the gas holder4    ,to accomplish this 
object1 the apparatus through which the 
gas passes  into the mains1 is provided 
with an aperture which is capable of    
being  enlarged or diminished by a very 

slight force4 ,to effect this object the
  gas is made to enter a small vessel1  
and then to pass through a  regulating  
aperture1 the capacity of which becomes 
enlarged or  diminished by the velocity 
of the gas to a certain standard4 ,if   
the  pressure of the gas in the gas     
holder becomes increased1 the regulating
  aperture through which the gas passes 
into the mains1 becomes  diminished1 in 
such a proportion1 that the velocity    
with which the gas  issues into the     
mains1 remains constant and uniform4    
,and on the other  hand1 if the pressure
 of the gas in the gas holder becomes   
diminished1  the regulating aperture of 
the governor becomes enlarged to effect 
the  intended regulation4    ,the       
following is a concise description of   
the manner in which this  instrument is 
constructed4    ,a1 ,b1 ,c1 ,d1 fig4 #i1
 pl4 ,,iii4 is a hollow cylindrical     
vessel1 or  the outer case of the       
machine4 ,it is made of sheet iron or   
copper1  japanned within and without1   

closed at the top and bottom4 ,it is    
placed  between the gas holder and the  
mains1 into which the gas is to be      
conveyed4 a1 x1 is a pipe which proceeds
 from the outer vessel and  branches    
upwards in the centre of the base of the
 outer vessel ,a1 ,b1 ,c1  ,d4 ,it      
brings the purified gas into the        
governor4 b1 ,t1 is the outlet  pipe    
which conveys the gas from the governor 
into the mains4 ,it is  placed above the
 inlet pipe and communicates with the   
interior vessel4  ,g1 ,h1 a short       
projecting hollow cylinder1 which       
proceeds downwards from  the centre of  
the base of the outer case of the       
machine ,a1 ,b1 ,c1 ,d4 u1  x1 y1 z1 is 
the regulator1 properly so called2 it   
consists of a  small conical vessel1    
also made of sheet iron or copper1      
closed at the  top and open at bottom1  
japanned within and without4 ,this      
vessel rises  and falls vertically in   
the outer cylindrical case4 ,a1 ,b1 ,c1 
,d1 of the  machine1 when the latter is 

filled with water4 ,it is kept steady in
 its  motion by two slender guide rods1 
as shewn in the sketch4    ,between the 
inlet pipe which conveys the gas into   
the governor1 and the  outlet pipe which
 conveys the gas into the mains1 is     
fixed horizontally  a partition plate1  
having a circular aperture in the       
centre4 ,this plate  is seen between the
 letters x1 ,t4    ,through this orifice
 passes a perpendicular axis ,p1 which  
is fixed at  the top in the centre of   
the regulator or interior floating      
vessel u1  x1 y1 z4    ,the interior    
extremity of the axis ,p1 is furnished  
with a cone1 having  its base downwards1
 and projecting beyond the pipe a1 x1   
into the  short cylinder ,g1 ,h4 ,the   
base of this cone slightly exceeds the  
diameter  of the orifice x1 ,t1 so as to
 close up entirely1 when the regulator  
is  raised to its greatest height in the
 outer vessel ,a1 ,b1 ,c1 ,d4 ,but when 
the floating vessel u1 x1 y1 z1 descends
 in the outer vessel ,a1  ,b1 ,c1 the   

vertex of the adjusting cone ,p1 is just
 entering the aperture4    ,the         
regulator is conical1 and its form is in
 exact proportion to the  loss of the   
weight of water which it displaces2 so  
that the gas conveyed  into it always   
retains an invariable density at        
whatever height the  regulator may be   
immersed in the water in the outer      
vessel4 ,if the outer  vessel be filled 
with water up to the top of the central 
branch pipe1  the interior vessel will  
float1 and the water will stand in the  
outer  vessel at the same height as in  
the inside of the regulator2 hence the  
density of the gas within will be the   
same as the outer air4 ,but the  density
 of the gas in the regulator may be     
increased at pleasure by  applying a    
weight to the top of the regulator1 the 
water will then stand  higher on the    
outside of the regulator than within1   
and this adjustment  will remain        
uniform1 because the quantity of matter 
of the regulator is  in the ratio of its

 specific gravity or loss of weight as  
it becomes  immersed in the water4      
,let us suppose that the pipe above the 
partition plate be connected with  a    
main1 and that the outlet pipe below the
 partition plate be connected  with a   
gas holder supplying gas into the       
machine2 it will be evident  that if the
 density of the gas in the inlet pipe   
becomes by any means  increased1 a      
greater quantity of gas must pass       
betwixt the sides of the  adjusting cone
 and the aperture in the partition      
plate1 the consequence  of which will be
 that the floating regulator will rise1 
and therefore  contract the area of the 
partition plate4 ,and if1 on the        
contrary1 the  gas in the inlet pipe    
decreases in density the regulator will 
descend1  so that whatever density the  
gas may at any time assume in the gas   
holders or mains1 its density in the    
floating vessel u1 x1 y1 z1  will remain
 uniform1 and consequently the velocity 
of the gas passing  into the mains will 

be regular4    ,for when the aperture of
 the partition plate would admit more   
gas than  what is necessary for the     
density of the gas in the mains1 the    
floating  regulator rises1 and by that  
means raises the adjusting cone to      
diminish  the aperture in the partition 
plate1 and when1 on the contrary1 the   
aperture does not allow a sufficient    
quantity of gas to come from the  gas   
holders1 the gas passes out of the      
regulator into the mains1 and in  so    
doing the regulator descends1 and       
consequently the adjusting cone         
increases the opening to admit the      
requisite gas into the mains4    ,the   
further application of this machine1 for
 regulating the height of  the gas      
flames issuing from burners or lamps of 
different kinds will be  shewn          
hereafter4      ,gas ,holder with       
,governor or ,regulating ,guage at the  
,gas ,works ,chester4    ,fig4 #g1 plate
 ,,vi41 exhibits a perpendicular section
 of the gas holder at  ,chester4 ,a1 ,a1

 are wooden beams or pillars fixed into 
sockets or shafts  constructed on the   
outside of the brick-work1 and          
descending as seen in  the design to the
 depth of the tank4 ,there are four of  
these pillars1  three only are seen in  
the section4 ,b1 ,b1 are round iron     
guide rods  rendered steady by stays at 
the upper extremity of the rods4    ,to 
the upper and lower edges of the gas    
holder are fastened eye bolts1  ,c1 ,c1 
through which the guide rods1 ,b1 ,b1   
are inserted1 so that the gas  holder   
must move steadily and firmly4 ,d1 ,e1  
are the inlet and outlet  pipes which   
convey the gas into and out of the gas  
holder4    ,f1 ,f1 are diagonal stays   
for supporting the roof of the gas      
holder1  which has a slope of ten feet  
from the centre to the circumference4   
,g1  is the wooden curb at the lower    
margin of the machine4    ,this gas     
holder is circular4 ,it measures        
forty-eight feet in diameter1  and      
thirteen feet in height2 its weight is  

eight tons4    ,the regulator adapted to
 this gas holder1 measures three feet   
across its  base1 and its height is     
three feet three inches4 ,the base of   
the  regulating cone is four inches1 and
 its length two feet4 ,the machine is   
made of sheet iron japanned within and  
without4      ,gas ,holder with         
,governor or ,regulating ,guage at the  
,birmingham ,gas  ,works4    ,the       
construction of this gas holder1 as     
exhibited plate ,v41 fig4 #b1  shows a  
perpendicular section1 and fig4 #c1 a   
plan of the machine2 a1  a1 a1 a1 fig4  
#c1 are upright pillars1 two of which   
,b1 ,b1 are seen  in the section1 fig4  
#b4    ,in the centre of the gas holder 
is fixed a pipe1 which allows the gas   
holder to slide on the central guide rod
 ,g1 made fast at the bottom of  the    
cistern1 and at the top of the cross    
framing4 ,c1 ,c1 are diagonal  stays2   
,d1 the inlet pipe which conveys the gas
 into the gas holder ,e2  the outlet    
pipe ,f1 the wooden curb4    ,the       

capacity of this gas holder is #cj1jjj  
cubic feet2 its regulator is  precisely 
similar to that before described4 ,the  
weight of the gas  holder1 exclusive of 
the wooden curbs at top and bottom1 is  
between  eight and nine tons4#ci        
#ci ,the gas holder without specific    
gravity apparatus1 at the ,bristol      
,gas ,works1 is constructed on a similar
 principle4 ,its capacity is    #dc1jjj 
cubic feet4 ,its regulator is like those
 already described4    ,the gas holder  
thus disencumbered of its specific      
gravity apparatus1  requires no building
 to enclose it1 it may be erected in the
 open air1  for the machine cannot      
suffer from the rain or snow falling    
upon it1 nor  can the action of the wind
 render the lights unsteady4    ,the    
saving which has been effected by these 
improvements is very great4  ,a gas     
holder without balance weight and       
specific gravity apparatus1 with  its   
governor1 may be erected complete for   
action1 for little more than  half the  

cost that would be required for the     
erection of an apparatus of  the same   
capacity constructed on the old plan4   
,the cheapest house constructed of sheet
 iron to surround a circular gas  holder
 of #ae1jjj cubic feet capacity1        
supposing the surface of its  cistern or
 tank to be level with the ground1 costs
 no less than 4 #cbj4  ,the balance     
weights and chains 4 #fj1 and the       
cast-iron framing for  supporting the   
specific gravity machinery 4 #aej4      
,the cost of a gas holder of the        
before-mentioned capacity1 will be 4    
#cjj1 and a cast-iron tank for it1 4    
#hjj4--;,if the tank be constructed of  
brick-work1 it will cost about 4 #ejj1  
and if of wood 7an iron-bound  vat17 it 
will cost 4 #fjj4    ,a governor or     
regulating guage adapted to a gas holder
 of from #aj1jjj to  #dj1jjj cubic feet 
capacity1 costs 4 #ej4 ,in the          
construction of the gas  holders1 as    
hitherto described1 it is always        
advisable when the  situation will admit

 it1 that the diameter to the height of 
the machine  should be in the proportion
 as three to two4 ,if these dimensions  
be  observed1 and the gas holder is not 
burdened by iron stays1 it will not     
displace a column of water more than one
 inch and a half in height4 ,and  by    
adapting to the machine1 a governor or  
regulating guage1 a  considerable saving
 will be effected4 ,the gas holder may  
then be  constructed as shown fig4 #g1  
plate ,,vi41 or fig4 #b1 plate ,v4 ,a   
circular  gas holder of #cj1jjj cubic   
feet capacity1 if properly constructed1 
weighs no more than eight or nine tons1 
including its wooden curb at its  lowest
 extremity1 and its diagonal stays4#dj  
#dj ,mr4 ,lee of ,manchester supplies   
his house1 two miles distance from      
the manufactory1 by means of a portable 
gas holder4#da ,a small    carriage upon
 springs conveys two square close gas   
holders made of    wrought iron plates1 
and each containing fifty cubic feet of 
perfectly    purified gas1 equivalent   

together to about six pounds of tallow4 
,each    gas holder weighs about #afj   
pounds2 and has a valve at the bottom1  
which is opened by the upright main     
pipe1 the moment the gas holder is      
immersed in the pit4 ,the strength of   
one man is found sufficient for    the  
labour of removing the gas holder from  
the carriage to its place4      #da     
,henry's ,experiments on the ,gas from  
,coal1 in the ,memoirs of the           
,manchester ,literary and ,philosophical
 ,society1 #ahai4    ,the roof of the   
machine ought to be constructed of      
thicker sheet iron  than those forming  
its sides4 ,the only object of the      
balance weight1 is  to counterpoise the 
weight of the chain of the gas holder of
 the old  construction1 so that when the
 gas holder is wholly immersed in the   
cistern1 the chain and balance weight   
are in equilibrium1 deducting the       
required pressure with which the gas    
holder is intended to act4 ,and this    
ought never to exceed from half an inch 

to an inch perpendicular head  of water4
    ,the sheet iron best adapted for    
constructing gas holders1 is that known 
in commerce as ,no4 #af1 wire guage4#db 
,gas holders made of plates of  iron of 
this kind1 have now been in use for     
upwards of nine years1 and  are not in  
the least injured or decayed4           
,self-interested views may  sometimes   
lead unprincipled workmen to make use of
 sheet iron plates of  a much greater   
thickness1 but experience has           
sufficiently shown that any  greater    
thickness than what has been specified  
is wholly unnecessary1  and only serves 
as a drawback to the facility of the    
general operation4      #db ,a          
superficial foot weighs three pounds4   
,revolving ,gas ,holder at the          
,westminster ,gas ,works4    ,the       
revolving gas holder is an ingenious    
contrivance invented by ,mr4  ,clegg1   
for storing large quantities of gas4 ,a 
gas holder of this  construction may be 
erected with advantage in situations    

where the  nature of the ground will not
 admit of a deep cistern either above or
  below the ground being constructed1   
without an enormous expence4    ,the    
base which it occupies is no larger than
 what would be required for  a gas      
holder of equal capacity1 built on the  
plan of the gas holders of  which       
descriptions have been just given4      
,it regulates its own specific gravity4 
,and though more expensive in the       
construction1 yet as it does not require
 a deep cistern1 like the  machines     
already described1 it can be erected at 
the same cost4 ,the  revolving gas      
holder is exhibited1 fig4 #h1 plate     
,,vi4 ,its capacity is  #ae1jjj cubic   
feet2 it weighs #ab tons4 ,plate ,i41   
7on the title page17  exhibits a        
perpendicular section of the gas holder4
    ,on inspecting fig4 #h1 plate ,,vi41
 it will be seen that this machine is   
the segment of a hollow cylinder1 or    
broad wheel1 formed by two  concentric  
cylindric surfaces of #bej each1        

revolving upon an horizontal  axis1 and 
supported upon a wooden frame or truss1 
in a brick cistern1 ,i1  ,k1 ,l4    ,the
 extremity ,c1 ,d1 fig4 #h1 plate ,,vi41
 or ,c1 plate ,i41 of the segment of    
the cylinder1 is open1 and the other    
extremity ,a1 is closed4 ,e1 is a       
balance pipe1 which connects the closed 
with the open extremity of the  machine4
    ,this pipe is made of such a weight 
as to counterpoise the interval  between
 the open and closed end of the gas     
holder1 so that the machine  may move in
 a segment of a circle equally1 in      
whatever position it may  happen to be  
placed1 and hence the gas will be       
discharged from the gas  holder with an 
uniform velocity4    ,the balance pipe  
,e1 is closed at the part where the     
letter ,e is placed2  ,h1 is a straight 
pipe1 which forms the communication     
between the  balance pipe ,e1 and the   
horizontal axis upon which the machine  
moves4  ,this axis is hollow3 it is     
supported by stays and braces1 as shown 

in  the design on the title page4 ,the  
cistern in which the gas holder moves   
is #g feet deep4 ,it must be evident    
that the gas being conveyed into  the   
open end of the hollow axis1 it will    
pass through the pipe ,h1 into  the     
balance pipe ,e1 and this being stopped 
up near ,e1 the gas will  proceed into  
the closed end of the gas holder4 ,the  
operation will  therefore be as follows3
    ,let us suppose the closed extremity
 of the machine to be at the surface  of
 the water in the cistern1 and the gas  
flowing through the axis as  described1 
the extremity of the machine will begin 
to fill1 and  consequently to ascend2   
the gas holder will therefore continue  
to move  upon its axis until the open   
end ,c1 ,d1 fig4 #h1 plate ,,vi41 or ,c1
 plate  ,i41 comes nearly to the surface
 of the water1 and when the gas is      
required to be discharged1 it will      
return through the same channel by      
which it entered4 ,a sufficient pressure
 is given to this gas holder for        

discharging the gas at the velocity     
required1 by means of a weight          
suspended to one extremity of a chain1  
passing over a pulley1 whilst  the other
 end is fastened into the groove of a   
small circle attached to  the stays of  
the machine1 as shown in the designs4   
,the circle is  graduated to express the
 capacity of the machine4 ,thus any     
degree of  pressure may be given to the 
gas1 and the gas holder will retrograde 
in  an arc describing #bgj of a circle1 
as the gas becomes discharged1 until    
the end ,a1 again arrives at the surface
 of the water4    ,the small curved pipe
 ,t1 plate ,i41 serves to let the common
 air escape  out of the angular         
extremity of the machine1 whilst filling
 with gas1  when the margin of this part
 of the machine becomes immersed in the 
water1 and to let the common air enter  
again1 when the gas holder is           
discharging its contents4    ,s1 plate  
,i41 is a friction sector1 upon which   
the axis of the machine  revolves4 ,the 

advantage of this contrivance is1 that  
the friction is  very much diminished4  
,the length of the friction sector is   
eight feet1  the diameter of the gudgeon
 or axis four inches2 therefore the     
space  described by its outer           
circumference and its centre is in the  
proportion  of #if to #d4      ,rule for
 finding the capacity of a ,revolving   
,gas ,holder of given  dimensions4      
,to find the capacity of a revolving gas
 holder1 of given dimensions1  take the 
area of the whole diameter1 then the    
area of the inner  cylinder1 multiply   
the difference by the length1 and from  
this deduct  one-fourth4                
,collapsing ,gas ,holder4    ,the       
collapsing gas holder is a still farther
 improvement by ,mr4 ,clegg1  on this   
part of the gas light apparatus1 and    
certainly of all the  contrivances which
 have been invented for collecting and  
storing up  large quantities of gas1    
this machine must be pronounced to be by
 far  the most simple1 economical1 and  

efficient4 ,the striking advantage of   
the revolving gas holder which we have  
just been describing is1 that it        
enables the dimensions of the tank to be
 very much diminished1 where the  nature
 of the ground will not admit of a      
cistern of great depth being  sunk1     
except at an extraordinary expence2 but 
the still superior feature  of the      
collapsing gas holder which we now come 
to describe1 is1 that it  may be        
constructed of any required capacity1   
and adapted to a tank or  cistern of    
such diminished depth1 as scarcely to   
deserve that name4 ,it  requires a sheet
 of water no more than #ah inches in    
height1 so that it  may be constructed  
in or upon ground of all descriptions1  
not only with  every possible facility1 
but at an immense saving of expence4    
,fig4 #a1 plate ,,vii41 exhibits a      
perspective view of this gas holder4 ,it
  is composed of#dc two quadrangular    
side plates joined to two end  plates1  
meeting together at top in a ridge1 like

 the roof of a house4  ,the side and end
 plates are united together by air tight
 hinges1 and the  joints are covered    
with leather1 to allow the side plates  
to fold  together and to open in the    
manner of a portfolio4 ,the bottom edges
 of  the gas holder are immersed in a   
shallow cistern of water1 to confine    
the gas4 ,by the opening out or closing 
up of the sides and ends of the  gas    
holder1 its internal capacity is        
enlarged or diminished1 and this        
variation of capacity is effected       
without a deep tank of water to  immerse
 the whole gas holder in1 as required in
 the ordinary  construction of rising   
and falling gas holders4 ,the collapsing
 gas  holder requires therefore only a  
very shallow trough of water to immerse 
the bottom edges of the gas holder to   
prevent the escape of the gas           
introduced into it4 ,the lower edges of 
the gas holder which dip in water  are  
made to move in an horizontal plane or  
nearly so1 when they are  opened1 so    

that they dip very little deeper in the 
water when shut or  folded together1    
than when opened out4      #dc ,from    
,mr4 ,clegg's specification--the same   
letters of reference    indicate the    
same parts in all the designs4    ,for  
this purpose the top or ridge joints    
which unite the two sides of  the gas   
holder1 are slightly raised up when the 
sides close or approach  together1 or   
slightly depressed when the sides open  
out or recede from  each other4 ,to     
guide the whole gas holder in this      
movement1 two  perpendicular rods rise  
from the bottom of the shallow tank     
which pass  through sockets in the ridge
 joints at the upper part of the gas    
holder4  ,these sockets are secured by  
collars of leather round the shafts or  
rods1 to prevent the escape of the gas1 
and they are braced by chains           
proceeding from their upper extremities 
and fastened at the ground on  each side
 of the tank4    ,the weight of the gas 
holder is balanced by levers bent in the

 form of  the letter ,l1 and placed     
inside of the gas holder4 ,these levers 
move on  centre pins fixed at the bottom
 of the shallow trough1 which pass      
through the angles of the ,l levers4    
,the perpendicular arms of the levers   
are jointed at their upper extremities  
to the sides of the gas holder1  nearly 
in the middle4 ,at the ends of the      
horizontal arms of the ,l  levers1 are  
weights to counterbalance the weights of
 the gas holder1 and  both sides of the 
gasholder are provided with these kind  
of levers1  which at the same time that 
they balance its weight cause the ridge 
joint of the machine to rise and fall1  
as before described1 so that the  under 
edges of the gasholder1 which are       
immersed in the water to confine  the   
gas1 must move in an horizontal plane   
instead of describing an arc  of a      
circle as they would do if the ridge    
joint was a fixed centre of  motion4    
,when the gas holder is closed the      
perpendicular arms of the levers stand  

nearly in a perpendicular position1 but 
when the gas holder is opened  out the  
levers become inclined4 ,and as they    
move upon a fixed fulcrum at  their     
lower extremities1 and are jointed to   
the sides of the gas holder  at their   
upper extremities1 they allow the whole 
of the gas holder to  descend gradually 
upon the guide rods1 nearly in the same 
degree as the  lower edges would rise up
 if the ridge joint was stable1 and if  
the  sides described an arc of a circle4
    ,it is obvious1 however1 that the   
latter movement is not very essential1  
but it is convenient and necessary to   
make a very inconsiderable depth  of    
water in the trough or tank serve the   
purpose it is intended4 ,it may  be also
 observed that the sides of the         
collapsing gas holder may be made  to   
unfold or open on a fixed ridge point as
 a centre of motion1 but it  will then  
require a considerable depth of water in
 the tank to keep the  lower edges of   
the sides and ends of the machine always

 beneath the  surface of the water1     
because the sides of the gas holder then
 describe  an arc of a circle when they 
are open4 ,fig4 #a1 plate ,,vii41 is a  
perspective view of the apparatus1 as it
 appears when partly filled with  gas4  
,fig4 #b1 plate ,,vi41 exhibits a       
perpendicular longitudinal section  made
 through the middle of the gas holder   
and tank2 fig4 #c1 plate ,,vi41         
represents a transverse section2 fig4   
#d1 plate ,,vi41 is an end view of  the 
machine1 and fig4 #e1 exhibits an       
horizontal plan or section of part  of  
the gas holder1 or one of its ends1 to  
show how the end plates are  jointed    
together1 and the leather applied to    
prevent the escape of the  gas4    ,a1  
fig4 #b1 is the inlet pipe which conveys
 the gas into the machine1 it  rises up 
perpendicularly through the water in the
 tank1 high enough to  prevent the water
 entering it4 ,b1 is the exit pipe for  
discharging the  gas into the mains from
 the gas holder4 ,it rises up nearly to 

the top of  the machine4 ,c1 ,c1 are the
 guide rods1 they are firmly fixed at   
their  lower extremities into a         
cast-iron framing ,d1 ,d1 beneath the   
bottom of  the tank4 ,the upper ends of 
these rods are kept steady by chains ,e1
 ,e1  fig4 #c1 and fig4 #d1 descending  
on each side of the gas holder1 and     
fastened at bottom to ,d1 ,d1 part of   
the same iron framing4 ,f1 ,g1 ,k1 ,k1  
are the balance 7or ,l7 levers which    
suspend or bear up the gas holders2     
they move on fixed centre pins supported
 in pieces a1 a1 fig4 #b1 and  #c1 of   
the framing ,d4 ,the upper end of the   
perpendicular arms are jointed  to the  
iron bars ,h1 ,h1 ,h1 see fig4 #b1 which
 are riveted to the side  plates of the 
gas holder2 they are united by knuckle  
joints ,w1 fig4 #f1  which allow the    
sides of the machine to approach each   
other till they  come together4 ,the    
arms i1 i1 of the bent levers ,f1 ,g1   
,k1 ,k1 fig4 #d1  are placed nearly at  
right angles to the other arms ,f1 ,g1  

fig4 #c1 and  the extremities of the    
arms i1 i1 are loaded with counterpoise 
weights ,k1 ,k1 which always tend to    
bring the arms ,f1 ,g1 into a vertical  
position1 and consequently to close up  
the sides of the gas holder1 in  order  
to expel the gas through the exit pipe  
,b1 fig4 #b4    ,three pairs of the     
above mentioned ,l levers are           
represented in fig4 #b1  in the length  
of the gas holder to support it in      
different parts and to  prevent it      
altering its figure4 ,the weight that   
must be used is  according to the       
magnitude of the machine4 ,the pairs of 
levers ,f1 ,g1 ,k1  ,k1 fig4 #c1 are    
placed side by side on the same centre  
pins1 and cross  each other4 ,k1 ,k1 are
 counterpoises at the ends of the arms  
i1 i1  they are long pieces of iron     
extending from one lever ,k1 to the next
  lever4 ,the tank is furnished at the  
bottom with a recess1 as seen in  fig4  
#c1 and #d1 to allow the arms i1 i1 and 
counterpoises ,k1 ,k1 to  descend       

beneath the edges of the gas holder4 ,in
 the course of the  movement of the     
machine1 the sides of the gas holder are
 shorter at the  top or ridge joints    
than at the bottom edges1 as seen in    
fig4 #b1 in  order that the under edges 
of the folding ends can move in an      
horizontal  plane4 ,each of the folding 
ends is made of two triangular plates1  
connected together by an air tight      
joint1 and each plate is again  jointed 
to its respective side plate1 and they  
are made tight by  introducing a piece  
of leather or oil-cloth1 or any other   
flexible  substance impervious to air in
 the angle at the joint4    ,fig4 #e1   
represents the end plates of the gas    
holder when nearly  extended1 but when  
it is closed up1 the two parts ,n1 ,o1  
of the end  assume the position as shewn
 by dotted lines4 ,l1 ,m1 fig4 #e1 shews
 how  the ends of the two side plates   
are turned outwards at b1 to render     
them stiff and firm4 ,as all the        
flexible joints are made strong by      

metallic joints or hinges1 the leather  
has no stress to bear but only to       
prevent the escape of the gas2 ,r1 ,r1  
fig4 #b1 are the collars of leather  to 
prevent the escape of the gas at the    
openings in the top or ridge  joint     
where the guide rods c1 c1 pass through4
    ,the tank must be filled with water 
to such a level that the under edges  of
 the sides and ends of the gas holder   
will be a few inches immersed in  the   
water4 ,the counterpoises ,k1 ,k1 fig4  
#c1 tend to close the sides of  the     
machine together1 and expel the gas from
 the gas holder through the  pipe ,b1   
fig4 #b4 ,the counterpoises are so      
adjusted in weight as to force  out the 
gas with the requisite pressure4    ,if 
more gas be introduced by the pipe ,a1  
it distends the sides of the  machine   
and moves them outwards upon the ridge  
joint4 ,a man hole1 as  seen at ,s1 fig4
 #b1 is made in each side of the gas    
holder1 to give  entrance when any      
repairs are necessary1 or to oil or     

examine the  joining leathers4 ,it is   
scarcely necessary to add that the form 
and  dimensions of this gas holder1 and 
the materials of which it can be made   
may be varied without any deviation from
 its essential properties as  they have 
been now described4 ,for instance1 the  
ends of the gas holder  may be formed of
 more than two folding plates1 united   
together1 if it is  judged necessary1   
and the levers ,f1 ,g1 may be varied in 
number1 form1 or  proportion1 provided  
they balance the weight of the sides and
 cause the  lower edges of the gas      
holder to move nearly in an horizontal  
plane4 ,or  the balance levers may be   
laid aside entirely1 and the gas holder 
may be  suspended from the upper part of
 the guide rods ,c1 ,c1 without moving  
up  and down thereon4 ,but in this case 
it will require more water in the  tank 
to keep the open end of the gas holder  
always immersed in the  water2 the      
weight of the sides of the gas holder   
will then tend more to  bring them      

together and to expel the gas4    ,in   
proportion as the quantity of water     
sufficient for the tank of the          
collapsing gas holder is less than that 
required for the tanks of other  gas    
holders1 it is attended with this       
further advantage1 that the water  can  
be let off or removed without any       
expence when repairs are  necessary4 ,if
 the repairs indeed are trivial1 they   
can be made without  letting off the    
water at all1 the depth being no more   
than one foot4 ,in  the case1 on the    
contrary1 of the gas holder1 with or    
without specific  gravity apparatus1 the
 quantity of water is so considerable1  
that the  means provided for carrying it
 off must always be attended with great 
difficulty and expence2 and yet it is a 
provision which is in all cases         
indispensable1 no matter however        
difficult or expensive1 for no material 
repair to the interior of the apparatus 
can be otherwise effected4    ,with     
regard to the best size of a gas holder 

adapted to a certain number  of retorts1
 it may be stated1 that this machine    
should be of a  sufficient capacity to  
hold the whole quantity of gas that is  
required  for the supply of the lights  
during one night1 exclusive of what may 
be  furnished by the retorts during that
 time4      ,rule for finding the       
capacity of a ,collapsing ,gas ,holder  
of given  dimensions4    ,the bulk of   
gas which a collapsing gas holder of    
given dimensions will  contain1 may be  
found1 by multiplying the area of the   
triangle contained  between the side    
plates when at their greatest extent1   
and the surface  of the water1 by the   
mean length of the side plate4 ,for     
example1 suppose  the base of the       
triangular end plate be #cj feet long1  
and #cj feet high1  and that the length 
of the side plate at the top be #dj     
feet1 and at the  bottom #fj feet1      
#cj  #ae  #dej area of end plate1       
#dej  #ej  mean length of end plate1    
#bb1jjj cubic feet capacity4#dd      #dd

 ,a collapsing gas holder of #bb1jjj    
cubic feet capacity1 costs    about 4   
#hjj1 it weighs eight tons2 a collapsing
 gas holder containing    #ae1jjj cubic 
feet1 which weighs seven tons1 costs    
about 4 #gjj1 and a    ditto containing 
#cj1jjj cubic feet costs about 4 #ajjj4 
,the depth of    the cistern for either 
is one foot4      ,reciprocating ,safety
 ,valve4    ,it must be sufficiently    
obvious that when the gas holder is     
full1 and  the distillation of the gas  
continues going on1 that unless a       
provision  is made for conveying away   
the surplus gas1 it must escape by      
bubbling  up from underneath the gas    
holder4 ,and should the gas holder      
happen to  be enclosed within walls1 the
 gas may by chance accumulate1 so as to 
give rise to serious accidents4    ,as a
 remedy for this evil the manufacturers 
of coal gas have until very  lately     
contented themselves with what is called
 a safety tube1 adapted  to the gas     
holder1 by which1 all the superfluous   

gas was carried away  into the open air2
 or by leaving large apertures in the   
roof or upper  part of the building1 for
 the ready escape of the gas4 ,by either
 of  these devices the danger from the  
accumulation of waste gas1 was in part  
only avoided1 and instances might be    
named where dangerous consequences      
ensued from an accumulation of gas1 in a
 confined atmosphere1 in the  vicinity  
of the upper part of the gas holder4    
,in some instances1 indeed1 recourse was
 had to the establishment of a          
communication between all the reservoirs
 and an auxiliary gas holder or  gas    
holders1 by means of a pipe furnished   
with an hydraulic valve2 but  this was  
an expensive arrangement which required 
personal  superintendance1 and depended1
 of course1 for its efficiency on the   
integrity and good conduct of the       
servant employed4    ,mr4 ,clegg has    
now1 however1 invented what has been    
termed the  ,reciprocating ,safety      
,valve1 which has a self-acting         

operation1 and by  which an exit for the
 surplus gas of any number of gas       
holders that may  be in action is       
provided to an unlimited extent4 ,a     
communication is  established between   
all the gas holders and a waste pipe1   
which  communication opens or closes by 
the action of the gas1 as occasion      
requires1 and which may be extended to  
any number of gas holders at a  trifling
 cost4    ,the apparatus has now been   
adopted at the greater number of gas    
light  establishments1 and has been     
uniformly found most efficient in its   
operation4 ,fig4 #i1 plate ,,vi41       
presents a perpendicular section of the 
apparatus2 h1 h1 h1 h1 is a small vessel
 made of sheet iron1  about eighteen    
inches in diameter1 and twenty inches   
deep1 closed at top  and open at bottom4
 ,it is inverted into an outer air tight
 vessel1 i1  i1 i1 i1 of double the     
height and rather greater diameter1     
which  is filled with water to a certain
 height2 ,d1 is a pipe communicating    

with the gas holders that are in action2
 this pipe branches upwards  through the
 bottom of the outer vessel1 i1 i1 i1 i1
 and reaches  a little above the surface
 of the water in the outer vessel4 ,e1  
is a  small pipe1 the upper extremity of
 which is sealed by means of an         
inverted sheet iron cup ,g1 the edge of 
which is submersed under the  surface of
 the water in the outer vessel1 i1 i1 i1
 i4 ,this pipe  conveys the waste gas   
into the upper part of any chimney4     
,for let us suppose that the gas holders
 become overcharged2 the gas must  then 
acquire an increased density before the 
wooden curb of the gas  holder ,g1 fig4 
#g1 plate ,,vi41#de at the lower        
extremity of the  overcharged gas holder
 can begin to rise out of the water4    
,but when the  elasticity of the gas is 
thus far increasing1 and before the curb
 can  wholly emerge out of the water1   
the small vessel h1 h1 h1 h1 of  the    
reciprocating safety valve1 ascends1 and
 consequently establishes a             

communication between the overcharged   
gas holder and the pipe ,d1 of the      
reciprocating safety valve4 ,the surplus
 gas thus passes into the waste  pipe   
,e1 ,e1 which had been before sealed by 
the inverted cup ,g1 and is  hence      
conveyed into the upper part of the     
chimney where it terminates1  so that no
 accumulation of gas can ever take place
 above1 or in the  vicinity of any gas  
holder4      #de ,every gas holder ought
 to have a wooden curb at the bottom4   
,it must be obvious on the other hand1  
that when the gas in any of the  gas    
holders has recovered its original      
density1 the reciprocating safety  valve
 will again be closed by the descending 
of the cup ,g4          ,,part ,x4      
,gas ,metre1 or ,self-acting ,guage1    
which measures and registers1 in the    
absence of the observer1 the quantity of
 ,gas produced in a given time1  from   
any given quantity of coal1 or consumed 
during a given period1 by  any number of
 burners or lamps4    ,for the invention

 of this machine we are indebted to the 
ingenuity and  talents of ,mr4 ,clegg1  
and undoubtedly1 of all the improvements
 with  which the new art of procuring   
light has been recently enriched1 there 
is none which has been attended with    
results more beneficial to the  interest
 both of the manufacturer and consumer  
of coal gas4    ,in this machine we see 
combined a standard or check on the     
conduct of  the workmen1 which enables  
the manufacturer of coal gas to assure  
himself of obtaining at all times the   
greatest possible produce from his      
establishment2 a measure by which he can
 deal the gas out to his  customers in  
whatever quantities they may require it1
 and an index which  registers the exact
 quantities furnished1 and thus serves  
as an  infallible account of debtor and 
creditor between the seller and         
purchaser of gas4    ,this machine1     
therefore1 performs at once all the     
duties of an overseer1  meter1 and      
book-keeper1 and performs them all so   

much more effectually1  that its        
operation is not dependant on matters so
 uncertain as the care  or integrity of 
servants1 but on unerring principles    
which are fixed and  incapable of any   
hidden misapplication4    ,the view in  
which this machine naturally demands our
 particular  attention is that in which 
as a standard of the work which ought to
 be  performed1 it enables the          
manufacturer to make sure of obtaining  
the  greatest possible produce from his 
establishment4    ,the gas metre serves 
this purpose in the first place by      
enabling the  proprietors of gas works  
to know what is the utmost possible     
quantity of  gas which can economically 
be obtained from any given portion of   
coal1  with a given portion of fuel1 in 
any given time4    ,it is necessary1 in 
every gas light establishment1 in order 
to know  whether as much gas is obtained
 as might and ought to be produced1 that
  it be previously ascertained by a     
series of experiments how much gas the  

species of coal used at the works is    
capable1 on an average1 of  producing1  
and such data it is obvious1 can only be
 obtained by means of  an apparatus1    
which1 like this gas metre1 shall take  
measure of the  quantities of gas       
supplied by the manufactory at all      
times1 and under  all circumstances4    
,it may1 perhaps1 be imagined1 that     
assays sufficient for that purpose      
might be made by means of a few retorts1
 or small experimental  apparatus1 or by
 noting down the quantity of gas        
produced at the works  during the time  
the valves which convey the gas into the
 street mains  are shut1 and during     
which time the capacity of the gas      
holders may  afford a rule for          
ascertaining the quantity produced4 ,but
 nothing can be  further from the truth2
 assays of this description to be       
practically  useful and to serve as a   
basis for the operations of a large     
establishment1 must be made on a scale  
of magnitude and be continued for  a    

considerable period of time as well as  
under every variety of  circumstances4  
,the quantity of gas obtained from any  
given quantity of coal1 varies so  much 
with the degree of heat applied1 and the
 circumstances under which  the         
decomposition of the coal is effected1  
that the solitary product of  any one   
period of time can afford no positive   
criterion for the product  of any other 
period4 ,a correct general conclusion1  
in short1 can only be  drawn from the   
result of experiments carried on        
uninterruptedly through  a succession of
 days and nights1 and such a continuity 
of experiments  could1 previous to the  
invention of the gas metre1 only be     
affected by  means of two separate gas  
holders1 one for measuring the gas as it
 is  produced1 and the other for        
receiving the gas after it is thus      
measured1  in order to its being        
transferred into the mains4 ,by the aid 
of a single  gas holder1 an             
admeasurement could obviously be        

effected only during the  time the      
valves which transmit the gas into the  
street mains are shut1  and this1 when  
the days are short1 as in the winter    
season1 the most  productive period of  
the whole year1 is only about eight     
hours out of  the twenty-four1 leaving  
nearly two-thirds of each day1 during   
which1 no  account could be taken of the
 quantity of gas produced at the works4 
,it deserves further to be observed1    
that when two gas holders are  employed1
 the utmost that can be effected by     
them1 is the admeasurement  of the gas  
produced1 while the distinguishing      
feature of the metre is1  that it not   
only measures1 but by its own action    
registers the quantity  of gas produced1
 or expended1 in any given time4    ,nor
 does the whole merit of this machine1  
in an economical point of  view1 consist
 in its thus furnishing the manufacturer
 with an infallible  criterion of the   
quantity of gas which ought at all times
 to be  produced2 for1 in the second    

place1 it enables him by the several    
experiments which have supplied that    
criterion1 to ascertain at what  least  
possible expenditure of fuel1 and in    
what space of time the  greatest        
possible quantity of gas can be         
produced4    ,the advantage of the gas  
metre1 in these additional respects1    
will be  sufficiently demonstrated by   
attending for a moment to the situation 
of  the manufacturer of coal gas1 when  
without any such protecting register4   
,suppose1 for example1 that the         
manufacturer desires to know whether his
  workmen have made during a given time1
 7say during the night71 the  quantity  
of gas which they ought to have produced
 from a given quantity  of coal1 or     
whether they have consumed no greater   
proportion of fuel for  its production  
than was absolutely necessary4 ,he may1 
upon examination1  find all the retorts 
in an excellent working state1 but      
whether they  have been so during the   
whole of the night1 or whether the      

requisite  quantity of gas has been     
really produced during the time that the
 valves  which convey the gas into the  
mains have been open1 is to him a matter
  of uncertainty4 ,the workman may1 as  
has been too often the case1 have       
neglected the fire during the night1 and
 on every such occasion1 in  order to   
bring back again the retorts to a proper
 working state1 as well  as to redeem   
the time lost1 he may have urged the    
heat to a degree of  intensity much     
exceeding the temperature best suited   
for the most  economical production of  
the gas4 ,and however injurious such    
irregular  modes of operating may be for
 the master's interest they are         
altogether  shrouded from his           
observation4 ,it deserves also to be    
noticed that the  loss occasioned by    
this irregularity of operating is not   
merely a loss  of fuel1 for in          
consequence of it the retorts1          
7particularly if  cast-iron retorts of  
the usual forms17 are liable to more    

injury in one  day than they would be   
during a whole week1 if properly        
attended4    ,when the proprietor of the
 establishment1 on the contrary1 has    
recourse  to the gas metre1 not one of  
all these evils can occur without being 
liable to certain and instant detection4
 ,from the data which preceding         
experiments on the productiveness of the
 species of coal used at the            
establishment have furnished1 the       
overseer of the works is always  enabled
 to determine1 from the portion of coal 
he finds used1 how much  gas ought to   
have been manufactured during any space 
of time that has  elapsed1 and also the 
portion of carbonizing fuel which was   
necessary  for the production of that   
quantity of gas2 and comparing these    
data  with the quantity of gas which the
 index of the gas metre announces has   
been produced1 he is enabled to         
determine by mere inspection1 in an     
unerring manner1 whether the workman has
 acted with that sedulous  attention to 

his duty which the economy of the       
establishment demands4    ,the many     
important advantages in short which the 
manufacturer of coal  gas derives from  
this machine1 considered as a standard  
or check on the  conduct of the workmen1
 may be summed up in this--that while1  
without  the aid of the gas metre1 no   
establishment can be possibly more      
exposed  to suffer from the ignorance of
 managers or the want of fidelity in    
servants1 than a gas manufactory1 there 
is none which is more  independent of   
either than a gas manufactory1 possessed
 of this  important apparatus4 ,nor can 
the amount of that possible loss be     
regarded as otherwise than extremely    
serious1 when attention is paid to  the 
difference in profit and loss between   
conducting the process of  manufacturing
 coal gas on a system founded on the    
deductions of  experience1 and an       
assiduous attention to keeping up a     
regularly  sustained temperature2 and   
conducting the process on a system of   

random  calculation and irregular       
working1--a difference1 which as appears
 from  the details already laid before  
the reader1 amounts in respect to the   
quantity of gas produced1 to from fifty 
to one hundred per cent42 in  respect to
 the waste of machinery1 to upwards of  
eighty per cent42 and  in respect to the
 consumption of fuel and time to a sum  
in the ratio of  the loss experienced   
under both these other heads4    ,the   
,second ,general ,point of ,view in     
which the gas metre claims our          
attention1 is1 its excellence as a      
standard of fair dealing between the    
seller and consumer of gas1 by enabling 
the former to supply the gas in         
whatever quantities it may be required1 
and serving1 at the same time1  as a    
self-acting register of the quantities  
furnished4 ,it is for this  purpose     
merely necessary to connect the gas     
metre with the pipe of  supply1 which   
conveys the gas to any burner1 or number
 of burners1 or  lamps1 and the index of

 the instrument will regularly announce 
the  precise quantity of gas which has  
passed through the machine during any   
period of time1 from one day to a number
 of years1 without requiring any        
particular sort of care whatever4 ,every
 person must have noticed how           
shamefully many individuals disregard   
the terms on which they have  contracted
 for a supply of gas1 some by means of  
the excessive flame  they keep up1 and  
others suffering the lights to burn     
hours beyond the  time stipulated and   
contracted with the gas light company   
which supplies  them4 ,the latter have  
officers1 it is true1 whose duty it is  
to check  such abuses as far as is in   
their power1 but having no right of     
access  to the premises of individuals1 
their vigilance can only extend to shops
  and places open to public view and of 
general access2 and to these1 of        
course1 but occasionally4 ,in short in  
every place where gas is supplied  on   
contracts to pay for burning it a       

limited time1 by means of certain  sized
 burners or lamps1 instead of according 
to the quantity actually  furnished1 the
 seller must always be in a greater or  
less degree1 and in  some cases wholly  
dependent on the care and honesty of the
 purchaser for  the protection of his   
commodity from waste and depredation4   
,but when on  the contrary the seller   
possesses1 as he now does1 by means of  
the gas  metre1 an infallible check of  
the exact quantity of gas consumed in a 
certain time1 and the purchaser is bound
 to pay for as much as he uses1  the    
former is relieved from every           
apprehension or chance of being         
defrauded1 and the latter is furnished  
with the same motives for  economizing  
gas as he would have for economizing oil
 and candles4    ,the manufacturer is   
certain of obtaining what he has a just 
right to1  value for the whole quantity 
of gas supplied1 and the consumer is    
assured that if he wastes the gas       
unnecessarily1 he must as he ought1  pay

 the price of his own carelessness or   
profusion4 ,equal justice is  done both 
to the consumer and seller1 and the     
public at large are at the  same time   
most materially benefited1 in as much as
 they are saved from  paying for the    
expence of that waste of gas by a few1  
which from the  former impossibility of 
tracing it to the offending parties1 was
  necessarily added to the whole cost of
 the gas1 and equally partitioned  upon 
all the individuals who made use of it4 
,the waste being now  transferred to    
those who occasioning the waste and     
ought alone in  justice to bear it1 the 
price of the gas to the equitable and   
honest  consumer1 is thus reduced to an 
equitable and correct measure of value4 
,the benefits of this invention have a  
yet wider range2 not only does it       
secure full value for the whole of the  
gas manufactured1 but it tends to  make 
the gas a greatly more marketable       
article4 ,for in the system of  charging
 for the supply of gas by the year1 half

 year1 or quarter1 and  at one common   
rate1 many individuals who are only     
occasionally in want  of gas lights1 or 
whose demand is irregular and uncertain1
 such as the  proprietors of public     
rooms1 theatres1 c4 are debarred of     
availing  themselves of this kind of    
illumination1 except at an expence quite
  disproportioned to what other more    
regular customers pay1 and out of all   
proportion of the value of the quantity 
of gas consumed by them4 ,the gas  light
 under such circumstances is not as it  
ought to be1 a light for  all4 ,it is   
not as oil and candle are1 a benefit    
which every one may  obtain who is in   
need of it1 and in such quantities as   
may best suit his  means and            
convenience4 ,one of the capital        
advantages1 of the gas metre1  however1 
is1 that it makes gas a substitute for  
oil and candles1  applicable under all  
circumstances1 and that it enables the  
manufacturer  without the least         
prejudice or chance of prejudice to his 

interest1 to  supply gas in whatever    
quantities it may be demanded1 and at a 
fair  proportioned price4    ,in        
speaking thus of the influence which the
 gas metre must have in  attending the  
beneficial application of the new       
lights1 we are not  unaware that        
situations may present itself where the 
action of the metre  might be impeded   
from the want of a sufficient pressure  
of the gas in  the pipe of supply       
connected with it4 ,but this can never  
be the case  except where the pressure  
of the gas in the pipe of supply is so  
low as  three-eighths of an inch of a   
column of water1 and in all such cases  
it  is only necessary to give a greater 
capacity to the wheel of the  machine1  
than would be necessary under other     
circumstances1 and this  will at once   
make up for the inferiority of pressure4
 ,in point of fact1  therefore1 no      
situation can occur1 where the          
application of the machine  may not be  
rendered available4#df      #df ,see    

directions to workmen1 for adapting gas 
metres1 p4 #bbi4    ,nor do the various 
advantages which have now been detailed1
 form all the  good that this important 
machine is capable of furnishing4 ,the  
gas metre  furnishes at its axis a power
 which has been ingeniously applied to  
put  in motion the shaft of the lime    
machine1 employed for purifying the gas1
  see fig4 #c1 plate ,,vii4#dg ,the     
importance of a power thus certain in   
its  operation1 and obtained free of    
expence1 must at once be obvious1 when  
it is considered that upon whatever plan
 the purifying apparatus or lime        
machine may be constructed1 it is       
absolutely essential1 that its  contents
 be kept constantly in motion1 in order 
to produce the desired  effect upon the 
crude gas1 which would otherwise pass   
away in an impure  state4      #dg ,the 
upper axis communicates with the        
agitating shaft of the lime    machine1 
and the lower axis is a continuation of 
the shaft of the gas    metre4 ,the two 

pullies are connected by a strap4       
,when the charge of keeping the         
agitating shaft of the lime machine in  
action1 is intrusted to a workman1 there
 is no positive security against  his   
occasionally neglecting his duty1       
whereas by applying the gas metre  to   
that purpose1 the manufacturer is       
assured beyond the possibility of       
deception1 that when gas is produced1   
that gas is as certainly purified1  and 
a saving is effected in point of labour 
of the expence of two men1  one during  
the day1 and one during the night4      
,description of the ,gas ,metre at the  
,royal ,mint ,gas ,works4    ,fig4 #d1  
plate ,,ii41 represents a perpendicular 
section of the gas metre4  ,it is placed
 between the purifying apparatus or lime
 machine1 and the  gas holder fig4 #h1  
plate ,,iii41 exhibits a front          
elevation2 fig4 #a1 plate  ,,iii41 a    
perspective view1 and fig4 #f1 plate    
,,iii41 a transverse section  of the    
machine4    ,it consists of a hollow    

wheel or cylinder1 made of thin iron    
plate1  revolving upon an horizontal    
axis1 in the manner of a grindstone2    
this  wheel is enclosed in a cast iron  
air tight case containing water4    ,the
 cylinder or wheel1 is composed of two  
circular channels1 #a and #b1  fig4 #d1 
plate ,,ii41 concentric to each other4  
,the larger or outer channel  #a1 is    
divided into three equal compartments1  
by partition plates1 marked  a1 as shewn
 in the design4 ,the compartments are   
provided with  hydraulic ducts or       
valves1 made at the upper part of every 
partition  plate a1 a1 a1 and by means  
of them a communication is formed       
between the larger concentric channel   
#a1 and the outer case in which the     
wheel revolves4    ,similar valves are  
also placed at the foot of each         
partition plate1 they  are seen near the
 letters a1 a1 a1 and by this means1 a  
communication is established1 between   
each compartment or chamber of the      
larger concentric channel #a1 and the   

smaller interior circle #b1 of the      
wheel4    ,on inspecting the design1 it 
will be seen that the valves are        
situated  in opposite directions to each
 other1 hence there can be no           
communication either between the inner  
smaller concentric channel #b1 and  the 
larger compartment of the wheel #a1 nor 
between the latter  compartment1 and the
 exterior case1 in which the wheel      
revolves1 except1  through the valves a1
 a1 a1 which form the communicating     
ducts4 ,it  will be seen also1 that     
these valves are carried from one       
chamber of the  machine into another1   
but in opposite directions2 the entry   
into one  chamber1 being in the opposite
 direction to the hydraulic duct1 placed
  in the other chamber4    ,from these  
particulars the action of the machine   
will be obvious4    ,let us suppose that
 the outer case 7which is marked in the 
sketch by a  black tint17 in which the  
wheel revolves1 be filled with water1 to
 about  an inch above the axis of the   

wheel1 and that gas is conveyed into the
  interior small channel1 by a pipe1    
passing along the axis1 so as to  allow 
the wheel to turn freely round1 and that
 the pipe is turned up at  right angles 
in the inner chamber1 and projects a    
little way above the  surface of the    
water1 as shewn in the design4 ,the gas 
then must enter  into the interior      
chamber of the wheel above the surface  
of the water1  and must press against   
the adjacent partition2 it will         
therefore cause  the wheel to turn      
round1 and in consequence of this       
motion1 the next  partition plate will  
press the gas against the surface of the
 water1 and  cause it to pass through   
the hydraulic opening1 in an equal      
quantity to  that1 which is introduced  
into the exterior chamber4    ,this     
alternate filling1 and discharging1 of  
the contents of each  chamber1 will take
 place once during every revolution of  
the wheel1 and  hence the number of     
times each particular chamber has been  

filled1 and  emptied of gas1 may be     
known4    ,in fact this machine performs
 the office of three revolving gas      
holders1  fixed on an horizontal axis1  
and moving in a cistern1 which is the   
outer  case of the machine4 ,one gas    
holder1 or one compartment of the       
machine1  is always in the act of       
becoming filled with gas1 another is    
emptying  its contents into the outer   
case1 from which it passes into the     
reservoir1 where it is to be stored up1 
or to the lamps1 where it is to  be     
burned1 and the third compartment is    
stationary1 or in an  equilibrium4 ,the 
wheel in any situation will therefore   
always have one  of its receiving1 and  
one of its discharging valves open1 and 
consequently it will revolve4    ,now to
 ascertain the quantity of gas          
discharged by one revolution of the     
wheel1 we need only to know the capacity
 of the chambers1 and add them          
together4 ,let us for example suppose1  
that each chamber contains #egf  cubic  

inches1 then one revolution of the      
wheel1 discharges a cubic foot  of gas4 
,to register the total number of        
revolutions which the wheel  makes in a 
certain time1 a train of wheel-work is  
connected with the  axis of the metre1  
see fig4 #h1 plate ,,iii42 it consists  
of a pinion  impelling a common train of
 wheel-work1 composed of any number of  
wheels4 ,the pinion on the axis of one  
wheel1 acts into the circumference  of  
the next wheel1 and the circumference of
 the wheel being as ten to  one1 it is  
obvious whilst the metre makes #ajj1jjj 
revolutions1 if the  series consists of 
six wheels1 the last wheel of the       
series1 will only  have made one        
revolution4 ,each axis of the wheels is 
provided with a  finger and dial plate1 
divided into ten parts1 therefore any   
number of  revolutions may be read off  
at any time by inspection betwixt       
#aj1jjj1jjj  and one4    ,the velocity  
with which the metre acts1 is of course 
in proportion to  the quantity of gas   

passing through it4 ,thus suppose there 
is a burner  or gas lamp connected with 
the machine1 of one foot capacity       
lighted1  which consumes four cubic feet
 of gas in an hour1 the gas metre       
performs  four revolutions per hour1 and
 so on for every number of burners or   
lamps1 not exceeding the number which   
the machine is calculated to  supply4   
,to render the construction of the gas  
metre more obvious1 we have at  fig4 #f1
 plate ,,iii41 exhibited a transverse   
section of the machine2 a1  is the outer
 case of the machine in which the wheel 
revolves4 ,b1 ,b1 the  outer or larger  
concentric chamber1 7marked #a1 in fig4 
#d1 plate ,,ii47 ,l1  the inner or      
smaller concentric chamber1 7marked #b1 
in fig4 #d1 plate  ,,ii47 d1 the index  
on the axis which passes through a      
stuffing box in  front of the machine4  
#e1 #e1 #e1 #e1 are stays or braces for 
supporting the  wheel2 they are likewise
 seen in fig4 #d1 plate ,,ii4 ,a1 is the
 inlet pipe  for the gas to enter into  

the machine4 ,the gas passes through the
 pipe  h1 and from thence into the      
curved pipe i1 into the interior chamber
  ,l1 of the metre4 ,the pipe h1 is     
surrounded by a second pipe ,k1 which   
has a small aperture at x1 the office of
 which is1 to act as a siphon1  in order
 to preserve the proper level of the    
water in the machine4 ,the  water is    
poured into the machine1 through the    
small funnel at the back  of the        
entrance pipe ,a4 y1 is a float1 which  
stops the performance of  the metre     
altogether1 if a fraudulent attempt     
should be made1 to stop  the registering
 of the metre1 by drawing off the water 
with which it is  charged4 ,in fig4 #a1 
plate ,,iii41 a1 is the inlet pipe2 b1  
the outlet  pipe of the gas2 and fig4   
#b1 shows the interior chamber4    ,the 
registering wheel work1 may be adapted  
to any part of the machine1  and the    
motion may be communicated by a mitre   
wheel1 from the shaft of  the machine to
 the index4    ,the gas metre at the    

,royal ,mint measures and registers     
#cj1jjj cubic feet  of gas every        
twenty-four hours4#dh      #dh ,the gas 
metre at the ,bristol gas works         
registers #fj1jjj cubic    feet of gas  
every twenty-four hours4 ,the metre at  
the ,chester gas    works registers     
#dj1jjj cubic feet every twenty-four    
hours4--,one of the    metres at the    
,birmingham gas works registers #dj1jjj 
cubic feet1 and    the other 7now       
erecting7 will register #ajj1jjj cubic  
feet every    twenty-four hours4        
,rule for calculating the weight1 which 
a ,gas ,metre of given dimensions1  will
 raise to a given height1 in a given    
time4    ,the following calculation will
 exemplify the power produced by a gas  
metre constructed to register #fj1jjj   
cubic feet of gas1 in a day4 ,the       
diameter of such a metre would be six   
feet1 its depth three feet1 and  the    
depth of its rim eighteen inches4       
,the section of the rim would therefore 
contain #fdh square inches1 and         

supposing the pressure of the gas       
passing into the machine to be equal  to
 a column of water two inches high1 its 
buoyant power would then be  equal to   
#abif cubic inches of water1 or forty   
pounds and a half weight4  ,the mean    
diameter of the metre is #d feet #f     
inches1 which multiplied by  three1     
gives the perpendicular height that     
forty pounds and a half  weight1 would  
be raised by each revolution of the     
metre4 ,the number of  revolutions1 in  
one hour which the metre makes1 is #dj1 
they would raise  forty pounds and a    
half1 #edj feet high in one hour4       
,such a power is more therefore than    
sufficient to keep in motion the  shaft 
of the lime machine4      ,gas ,holder  
,valve1--,siphon1 or ,water ,reservoir4 
,this name is given to the principal    
hydraulic valve1 by means of which a    
communication is established between the
 gas holder or gas holders1 and  the    
principal pipe1 leading to the mains4   
,fig4 #g1 plate ,,iii41 exhibits a      

section of this valve4 ,it is composed  
of  an air tight box1 ,a1 ,a1 ,a1 ,a1   
containing a portion of tar1 or water2  
d1 is the inlet pipe which communicates 
with the gas holder1 ,b the  outlet     
pipe2 which conveys the gas into the    
mains4 ,c1 ,c1 is an inverted  cup1     
furnished with a sliding rod1 passing   
through a stuffing box1 so  that by     
means of the rod1 the cup may be raised 
or depressed4 ,for it is  obvious that a
 communication will be established      
between the inlet pipe  d1 and the      
outlet ,b1 when the cup is raised above 
the surface of the  tar or water in the 
box ,a2 and that the communication will 
be cut off  when the cup is depressed   
into the tar4 ,in the latter position   
the cup  is shewn in the design4 ,the   
sliding rod which raises and depresses  
the  cup1 passes through a frame ,e1 ,e1
 affixed to the upper part of the box   
,a1 and which serves as a guard for the 
rod1 so that it may be locked by  means 
of a cutter passing through the sliding 

rod1 and the frame of the  box4    ,fig4
 #c1 plate ,,iii41 exhibits a similar   
valve1 which at the same time may  be   
used as a water reservoir1 commonly     
called a siphon1 for  collecting the    
water that may happen to accumulate in  
the mains1 a  provision which it is     
essential should be made at the lowest  
place1  where two or more pipes incline 
towards each other4 ,for it is obvious1 
that if a fluid should happen to        
accumulate in the angular part1 where   
two descending pipes meet1 to a height  
sufficient to fill the angular  point1  
the communication between the two pipes 
would be completely cut  off1 so that   
the gas could not pass4 x1 x1 x1 x1 fig4
 #c1 is the  reservoir2 ,a1 the inlet   
pipe2 ,b1 the outlet pipe2 b1 a short   
cylinder  communicating with the exit   
pipe ,b1 it is open at bottom and closed
 at  top4 ,d1 d1 the hydraulic cup      
which1 when raised by means of the      
spindle e1 closes the exit pipe ,b1 by  
the open end of the cylinder  b1        

becoming immersed in the tar or water   
contained in the cup ,d1 d4  ,the darts 
show the course of the gas when the     
valve is open3 f is a  small pipe       
furnished at top with a screw and       
covered with a cap2 by  attaching a hand
 pump to this pipe1 the superfluous     
portion of fluid  that may have         
accumulated in the reservoir1 may be    
removed4 c1 c1 is  the equilibrium pipe1
 it connects the exit pipe ,b with the  
inlet pipe  ,a1 when the stop-cock with 
which it is furnished is opened4 ,this  
pipe  prevents the tar or water from    
being blown out of the hydraulic valves 
that may be interposed between the      
different descending mains of a         
district1 as would otherwise happen1 in 
consequence of the sudden  concussion   
that takes place when the main or gas   
holder valves are  opened4 ,because the 
gas in the mains1 and the gas in the gas
 holders1  are not in equilibrium4 ,but 
by means of the small pipe c1 c1 the    
equilibrium is obtained when the        

stop-cock of the pipe c1 c1 is  opened1 
and this should always be done before   
the main or gas holder  valves are      
opened4 ,for by neglecting this         
condition1 the water or tar is  liable  
to be blown out of all the hydraulic    
valves1 that may happen to  be          
interposed in the system of the pipes   
for conveying the gas1 and              
communications are thus opened1 which   
were intended to be shut4               
,,part ,,xi4      ,governor or          
,regulating ,guage4    ,the governor or 
regulating guage1 the construction of   
which has already  been detailed1 page  
#aga1 we shall here consider as an      
instrument by  means of which the gas   
flames of lamps and burners are kept of 
one  steady and uniform magnitude4      
,the velocity of the gas in the mains   
and pipes of supply1 is in the  first   
instance as various as there are        
differences in the altitude and  extent 
of the mains and pipes of supply4 ,a    
main1 at one place will  furnish with a 

certain pressure of gas1 a flame one    
inch high1 while at  a different        
altitude it will furnish a flame double 
that height4    ,if again the direction 
of the pipe has many turns or angles1   
and  contractions1 the velocity of the  
gas will be different on that account1  
than if it were direct and uniform4 ,and
 if the pipe is of any great  length1   
and of an uniform bore1 but unequally   
furnished with veins or  branch pipes at
 certain parts1 the burners will be very
 unequally  supplied with gas1 those    
which are near its head will be supplied
 with a  fuller stream of gas1 than     
those which are situated towards its    
termination4    ,and independent of     
these differences thus arising from     
diversity of  local positions1 there    
will always be one grand variety in the 
velocity  of the gas1 occasioned by the 
variety of periods during which lights  
are  required by different individuals  
supplied from the same main or system   
of pipes1 as for example3 when a certain

 number of burners are to be  supplied1 
and it happens that one half of these   
burners are shut sooner  than the rest1 
then in consequence of this1 the        
velocity of the gas in  the mains will  
be materially altered4    ,the          
inequality thus occasioned1 may be seen 
particularly exemplified in  the case of
 houses situated in the vicinity of any 
large establishment1  such as either of 
the great theatres of the metropolis1   
and supplied  with gas from the same    
mains4 ,while the theatres are open1 the
 lights in  the adjacent houses are low 
and feeble1 often too much so for the   
necessary purposes of the consumer1 but 
the moment the theatres are  shut1 the  
great quantity of gas which they        
previously carried off1 being           
transferred to such of the private      
houses as continue to be lighted1 the   
gas flames at the latter are raised to  
an extravagant height1 and burn  with an
 intensity which makes the gas light    
partake more of the  character of a     

nuisance than of a benefit4    ,it may  
be necessary for the better appreciation
 of the extent of this  nuisance to     
observe1 that it does not arise merely  
from the excess of  light produced1 but 
from the imperfect combustion of the    
gas1 and hence  a disagreeable odour is 
produced4 ,when the flame is suffered to
 rise  beyond the standard height1 the  
combustion of the gas becomes imperfect1
  part of the gas passes through the    
flame unburnt1 and occasions the  source
 of the offensive odour alluded to1     
which the gas lights never  produce when
 the combustion of the gas is complete4 
,the remedy for all  these              
inconveniences thus resulting from the  
various degrees of  velocity of the gas 
in the mains1 is to be found in the     
instrument now  under description4      
,the effect of this machine1 as already 
mentioned1 is1 that it causes the  gas  
to issue from the aperture of the       
burners or lamps with one uniform       
velocity1 whatever may be the variations

 which take place in the  pressure which
 urges the gas to pass through the pipes
 of supply4 ,and  such is the efficiency
 of the operation of the machine1 that  
it  regulates the flow of the gas       
through any burner1 tube1 or opening1   
with  a greater degree of exactness1    
than the centrifugal apparatus1         
regulates  the action of the steam      
engine4    ,the construction of the     
regulator to effect this purpose is     
precisely  similar to the apparatus     
already described1 page #aga4 ,when     
applied for  regulating the magnitude of
 the gas flames1 it is of course usually
 made  much smaller1 of iron plates1    
japanned within and without4 ,fig4 #d1  
plate  ,,iii41 exhibits a perspective   
view of the machine2 a1 is the inlet    
pipe1 b1 the outlet pipe2 ,p1 is the    
regulating cone1 passing through  the   
regulating aperture x1 ,t4 ,the floating
 vessel u1 x1 y1 z1  receives the gas   
introduced into the machine2 ,a1 ,b1 ,c1
 ,d1 is the outer  air tight case of the

 regulator4      ,directions to ,workmen
 for fixing the ,governor and ,gas      
,metre4#di      #di ,copied from        
,messrs4 ,clegg's and ,crossley's       
printed directions to    workmen1 for   
fixing governors and gas metres4    ,the
 governor must be fixed perpendicularly1
 so as to admit its floating  vessel u1 
x1 y1 z4 ,fig4 #d1 plate ,,iii41 or fig4
 #i1 plate ,,iii41 to  be taken out of  
the outer case of the machine if        
occasion should require  it4    ,the gas
 enters into the machine from the street
 mains at the lowest  branch a1 and     
passes out of the machine by its highest
 branch b4    ,in connecting the pipes  
of supply1 particular care must be taken
 that  the work is not bound1 or the    
governor by any means rendered leaky4   
,it  must be filled with water to the   
top of the central tube4    ,examine the
 workmanship of the machine to see that 
it is perfect1 and  that the regulating 
cone ,p1 is firmly secured to the top of
 the  floating vessel and well centered4

 ,the floating vessels u1 x1 y1  z1     
should clear the sides of the outer case
 of the apparatus by a  quarter of an   
inch2 and when sunk down1 it should rest
 even upon the top  of the central pipe1
 which conducts the gas into1 and out   
of1 the  machine4 ,the aperture in which
 the cone moves will then be at its     
widest  opening1 and when the floating  
vessel u1 x1 y1 z1 has risen to  its    
highest elevation1 the regulating       
aperture x1 ,t1 will be closed4    ,in  
this situation particular attention must
 be paid1 that the regulating  cone does
 not stick or rub in any part1 but that 
it descends freely4    ,to the lower    
extremity of the floating vessel u1 x1  
y1 z1 may be  adapted an air vessel for 
the purpose of reducing the pressure of 
the  gas4    ,the governor must be so   
fixed1 that the water which may condense
 in the  pipes leading to the burners   
shall drain back to the street mains1 in
  order that it may not accumulate in   
the machine so as to impede its         

operations2 for this purpose the gas    
pipes should have a fall of half an     
inch in three or four feet4    ,when the
 locality of situation will not admit of
 the water that may  accumulate in the  
pipes falling back to the mains1 its    
accumulation  within the governor above 
the proper level of the water is        
prevented by  an inverted siphon affixed
 to the machine1 which allows the water 
to  drain off without any escape of the 
gas4    ,the governor must be firmly    
fixed to the nearest beam or wall1 as   
the  least vibration will render the    
lights connected with it unsteady4      
,when a situation cannot be obtained    
sufficiently warm to prevent the  water 
from freezing1 the machine must then be 
wrapped round with woollen  cloth1 or   
any other bad conductor of heat4 ,the   
cellar where the gas  enters the house1 
has generally been found the most       
convenient  situation4    ,for supplying
 any deficiency of water which the      
governor may require2 a  small funnel   

with a curved tube is placed for this   
purpose at the top of  the governor4    
,when the governor is filled to its     
proper height1 the  water will begin to 
run out of the siphon4    ,the mode of  
regulating the height of the flames will
 be stated  presently4    ,fig4 #aa1    
plate ,,iii41 exhibits a portable       
governor or regulating guage1  combined 
with a gas metre in one case4 ,a1 is the
 inlet pipe which  conveys the gas into 
the machine1 and ,b1 is the pipe leading
 from the  governor to the lamps or     
burners4 ,d1 a label expressing the     
quantity of  gas discharged by one      
revolution of the wheel1 and the number 
of lights  which the metre is capable of
 supplying when the pressure of the gas 
in  the inlet pipe is of a density      
sufficient to support a column of water 
of half an inch in height4    ,in those 
situations where the pressure of the gas
 is equal in density to  support only a 
column of water one-quarter of an inch  
in height1 a metre  of a larger capacity

 must be adopted for supplying the same 
number of  lights2 and if the pressure  
of the gas be equal only to support a   
column  of water one-eighth of an inch  
in height1 the capacity of the metre    
must  be still larger1 and thus the     
capacity may be increased so as to equal
  every pressure that may occur4 ,the   
index which registers the number of     
revolutions1 and consequently the       
quantity of gas which passes through    
the metre1 is shut up in the projecting 
case1 near ,h1 furnished with a  lock   
and key4    ,previously to the gas metre
 being filled with water1 ascertain that
 the  regulating cone is screwed        
perfectly air tight into the top of the 
floating vessel which receives the gas1 
and that the regulating aperture  in    
which the cone moves1 together with its 
spindle and guide rods1 work  perfectly 
free and without friction4 ,raise the   
floating vessel to its  highest         
elevation1 thereby closing the          
regulating aperture suddenly with  the  

cone2 in this situation it must not rub 
when turned and tried on  every side1   
but descend with the least friction4    
,the gas metre and regulator being thus 
examined and fixed1 the machine  may be 
supplied with the requisite quantity of 
water in the following  manner3    ,open
 the stop-cock which admits the gas into
 the machine2 open also the  aperture   
,e1 which serves to show the pressure of
 the gas in the machine1  and likewise  
the opening ,g1 which lets out the air  
whilst water is  poured in at the       
aperture ,h4 ,the superfluous quantity  
of water will run  out by the siphon    
tube at ,k4    ,pour water also into the
 governor until it runs out at the      
aperture at  ,m2 and when this has been 
accomplished1 till the gas metre with   
water  at the opening ,h1 until it      
overflows at the aperture ,k1 when the  
surface  of the water will appear at the
 cypher line on the scale board4 ,the   
apertures ,f1 ,g1 ,h1 ,k1 and ,m1 may   
then be closed1 and the machine is      

ready for action4    ,near to ,n1 is an 
aperture communicating with the stuffing
 box in which  the axis of the machine  
moves1 and through which it should      
occasionally  be supplied with a small  
portion of melted tallow4    ,to adjust 
the height of the gas flames of the     
burners1 so that they be  all uniform1  
open the stop-cock which admits the gas 
into the metre1 and  open also the      
stop-cocks of the burners1 and as soon  
as the air has  become discharged by    
means of one or two revolutions of the  
metre1 light  all the burners4 ,adjust  
the height of the flames in the first   
instance  by their stop-cocks1 that they
 become all of an equal height1 which   
should be about double the diameter of  
the flame2 if any of the flames  be too 
low when the stop-cock is fully open1 a 
small weight must be  placed upon the   
top of the floating vessel of the       
regulator1 sufficient  to produce the   
required flame at the burner1 and then  
again adjust the  remaining lights by   

their stop-cocks as before stated2 this 
being done1  the aperture to which each 
burner is screwed must be sufficiently  
narrowed1 that it will admit no more gas
 than is requisite for the  required    
height of the flame1 when the stop-cock 
is fully open4 ,the  diminution of the  
aperture of the stop-cock may be        
effected by a brass  plug fitted into   
it1 with a hole in its centre1 which    
must be gradually  widened with a drill 
until the flame has required the proper 
height4 ,it  is recommended1 instead of 
adding weight to the floating vessel of 
the  regulator1 that the tubes which    
supply the gas be sufficiently capacious
  to render the weight unnecessary4     
,the burners should also be examined    
from time to time4 ,observe that the    
plugs1 sockets1 and every other part of 
the gas metre and regulator be  air     
tight1 and that there be no escape of   
water or gas4    ,an escape of gas1     
either from the metre or from any of the
 tubes or  burners1 will be discovered  

by looking at the index of the metre1 as
 the  wheel cannot fail to move whenever
 there is an escape of gas1 if the      
stop-cock is open which supplies the gas
 to the metre4 ,the place where  the gas
 escapes will be found in the usual way1
 either by the odour  which the gas     
produces1 or by passing a lighted taper 
over the apertures  and connections of  
the metre1 and along the tubes leading  
to the  burners1 which will cause the   
gas to take fire at the place where the 
leak happens to be4    ,the following   
remarks will assist the workmen in      
correcting any  irregularities which may
 occur in the lights connected with the 
apparatus4    ,a diminution1 or         
extinction of the lights1 may be        
occasioned by a  deficiency of water in 
the gas metre or regulator2 when this   
occurs the  necessary quantity of water 
must be supplied as before directed up  
to  the cypher line on the scale board  
,e1 of the metre1 and opening the       
aperture ,m1 where it may be seen when  

the water has risen to the proper       
height in the governor4    ,a diminution
 of light may also be occasioned by some
 obstruction or  contraction of the     
tubes which supply the gas1 or by a     
diminution of the  pressure of the gas  
in the mains1 to which the metre was    
originally  adjusted4    ,when the      
lights increase above their standard    
height1 and are variable  with the      
changes in the pressure or velocity of  
the gas in the mains or  tubes of supply
 within the house or place1 lighted1    
there is then reason  to believe that   
the governor is not performing1 which   
may arise from the  following causes4   
,its floating vessel u1 x1 y1 z1 may    
have  become fast by the friction of the
 spindle or guide rod1 requiring        
cleaning1 or by an accumulation of water
 in the air-vessel of the  floating     
vessel u1 x1 y1 z4 ,the water may be    
drained off at a  small plug by taking  
out the floating vessel4 ,the same      
inconvenience  would arise from a       

diminution in the proper level of the   
water4    ,in order to ascertain that   
the governor performs correctly1 observe
 at  the time of lighting or            
extinguishing any of the burners        
connected with  it1 that its floating   
vessel rises and falls every time the   
stop-cock is  opened1 and that the      
lights do not suffer any material       
change4    ,an instantaneous starting or
 dancing of the lights1 is generally    
occasioned by an accumulation of water  
in the tubes through which the  gas     
passes2 if this should happen in the    
vicinity of the metre and  governor1 it 
may be drained off at the aperture ,k4  
,a provision for a  like purpose is also
 made at the bottom of the governor when
 detached  from the metre4    ,in order 
at any time to ascertain the pressure of
 the gas in the metre1  close the       
stop-cock which admits the gas1 and open
 the aperture ,g and ,f1  which will    
shew the level of the water on the scale
 board ,e4 ,this being  first observed1 

close the aperture ,g1 and open the     
stop-cock1 and the  pressure of the gas 
in the metre will be indicated by the   
rise of the  water on the scale board   
,e1 above its original height4          
,,part ,,xii4      ,gas ,mains1 and     
,branch ,pipes4    ,the name of mains1  
is given in the strictest sense of the  
word1 to the  cast-iron pipes from two  
inches in diameter and upwards1 placed  
under  ground1 for conveying the gas    
into smaller branch pipes2 but in a more
  extended sense1 the term is applied to
 every pipe from which smaller          
ramifications or branch pipes proceed4  
,all mains destined to convey coal gas  
should be proved1 they should be        
submitted to the trial of sustaining a  
column of water #cjj feet high1  and the
 pipe should be rejected if the least   
moisture appears on any  part of the    
side of the pipe whilst submitted to    
this trial4 ,for  although such a pipe  
may remain impervious to gas for some   
time1 the  imperfection or fissure which

 permits the water to issue through     
under  such a pressure1 speedily        
increases1 in consequence of the        
moisture to  which the main under ground
 must necessarily be exposed4 ,a skilful
  workman who is in the habit of proving
 pipes will distinguish1 with an        
astonishing degree of correctness1 a    
faulty pipe1 by the sound produced  by  
blows of the hammer upon the pipe4 ,the 
faulty part1 when struck upon1  produces
 a jarring sound very different from the
 clear sound which a  blow of the hammer
 produces when the pipe is in a perfect 
state4 ,by this  means the workman also 
detects1 by the ear1 inequalities in the
  thickness of the metal of the pipe4   
,fig4 #ad1 plate ,v41 represents a      
longitudinal section of two flanch      
pipes1 and the mode of connecting them4 
a1 and b1 are the pipes with  their     
flanches connected2 they are joined     
together1 and rendered  air-tight1 by   
first interposing between the flanches a
 coat of iron  cement1 and then screwing

 up the faces of the flanches by means  
of screw  bolts and nuts4    ,the       
composition of the cement is as follows3
    ,take four ounces of flour of       
sulphur1 and two of muriate of ammonia1 
and  mix them intimately together4 ,when
 the cement is wanted1 take five  ounces
 of the above mixture1 and add to it six
 pounds of cast iron  borings1 and blend
 them intimately together in a mortar2  
wet the mixture  with water1 and when   
brought to a proper consistence1 apply  
it to the  joints with a wooden or blunt
 iron spatula4    ,a degree of action   
takes place among the ingredients and   
the iron  surfaces to which it is       
applied1 which at last causes the whole 
to unite  into one mass4 ,in fact1 after
 a time1 the mixture and the surfaces of
  the flanches become a species of      
pyrites 7containing a very large        
proportion of iron7 all the parts of    
which cohere strongly together1 and     
form one mass4 ,it is essential that no 
larger quantity of the  ingredients of  

the cement should be mixed up with      
water1 than is  required for immediate  
use4    ,fig4 #ae1 plate ,v41 represents
 a longitudinal section of a spigot and 
faucet pipe4 ,these pipes are most      
commonly used as gas mains4 a1 is       
called the spigot1 b1 the faucet4 ,the  
cavity between the inside of  one1 and  
the outside of the other1 is partly     
filled with rope yarn1 or  oakum1 and a 
good fitting of the two pipes being thus
 effected1 melted  lead is poured into  
the cavity1 which when set1 is hammered 
in by the  end of a punch4    ,the inner
 parts of the faucet of these pipes     
ought to be no larger in  diameter than 
just to fit the spigot4 ,this supports  
the pipe1  independently of the         
interposed lead and rope yarn1 and      
prevents the  risk of hurting the joint 
from any external stress4 ,the inner    
faucet is  commonly made about two and a
 half inches deep1 and has the spigot   
inserted one and a half inch into it4   
,the practice of some manufacturers  is 

to make the outer faucet1 or that which 
contains the lead six inches  deep1 for 
all pipes above six inches in diameter2 
and to make the  faucets of all pipes   
below six inches1 the same depth as the 
diameter of  the pipes4 ,it is usual to 
make the space for the oakum and lead   
all  round the spigot1 from one inch to 
one and a quarter inch2 that width is   
required1 in order that the lead may be 
firmly driven into the joint4  ,when the
 space is very narrow1 this cannot be   
done4 ,on the other hand1  when too     
wide1 there is a waste of lead1 and a   
risk of injury from the  unequal        
expansion of the two metals4    ,all gas
 mains laid in public streets should be 
placed at least eighteen  inches below  
the surface of the ground1 to secure    
them from being  disturbed by carriages1
 or interfering with the paving of the  
street2  they should be placed perfectly
 firm1 so that they may not easily give 
way4    ,the course of all gas mains    
should be rectilinear1 with a dip of    

about  one inch1 in every ten feet      
distance4    ,in all wide streets1 where
 the number of houses on both sides of  
the  streets1 to be supplied with gas1  
is numerous1 it is more economical to   
employ a separate gas main for each side
 of the street1 than to make use  of one
 larger main for both sides2 because    
smaller mains may then be  employed1 and
 the collateral branch pipes leading    
into the houses are  shorter2 these     
circumstances amply compensate for the  
additional main4  ,all branch pipes     
proceeding from a main1 should have a   
dip of about  one inch in ten feet1     
towards the main from which they        
proceed1 so that  any fluid that may    
happen to collect in these pipes must   
run into the  mains4    ,all small      
wrought iron branch pipes proceeding    
from the mains into the  houses or      
places to be lighted with gas1 should be
 covered with a thick  coat of coal tar1
 before they are laid down into the     
ground2 this may  easily be done by     

heating the pipe1 and laying on the     
boiled tar with a  brush4    ,every     
separate length of branch pipe should be
 tried by condensing the  pipe under    
water1 in order to be certain that the  
pipe is sound4 ,the  junctures of these 
pipes should be made by dipping the male
 screw of the  pipe into a mixture of   
white lead and linseed oil1 before they 
are  screwed together4                  
,notwithstanding the usual care which   
can be taken in proving pipes1  before  
the gas is admitted into them1 a slight 
leakage may be sometimes  subsequently  
detected4    ,therefore1 before the gas 
is suffered to enter the mains1 they    
should be  again proved1 in order to be 
certain that all the junctures are air  
tight4 ,the most convenient manner of   
proving the mains when laid1 is by      
means of a small portable gas holder    
filled with common air1 and  connected  
by means of a small pipe1 with the      
system of the mains to be  tried4 ,this 
gas holder should be made to act with a 

pressure at least  four times greater   
than the pressure which the pipes will  
have to  sustain by the gas they are to 
convey4 ,if the mains are air tight1 the
  gas holder will remain stationary1 but
 if they are not sound1 the gas  holder 
will descend1 in proportion to the leak 
of the mains1 the  quantity of gas lost 
may be thus ascertained4    ,every      
quarter of a mile of pipe should thus be
 tried separately4 ,in this  manner we  
become also enabled to detect instantly1
 whether any  collateral branch pipe has
 been left open by the workmen1 a       
neglect by  no means uncommon in this   
department of the gas light business4   
,in order to guard against the danger of
 water entering from the external       
surface into the pipes1 a reservoir     
should always be placed at the  lowest  
point1 where two or more descending     
mains meet and form an angle1  so as to 
receive the water that may happen to    
collect at this angular  point1 an      
accumulation of which would cut off the 

communication between  the two pipes2   
this reservoir is usually called a      
siphon1 see page #bba4  ,it ought to be 
at least twice the diameter of the bore 
of the mains1  between which it is      
interposed1 and four times that diameter
 in depth4  ,these reservoirs afford the
 best indication to show the sound or   
leaky  state of the system of the mains4
 ,in all instances where the pipes are  
perfectly sound1 observation has shown1 
that half a mile of gas mains1  three   
inches in the bore1 does not deposit    
more than a quart of water in  a year2  
on the other hand1 if the mains are     
leaky1 the water of the  reservoir      
requires to be pumped out1 sometimes as 
frequently as every  fortnight1 and     
during wet weather1 much oftener4 ,the  
loss of gas by such  leakage is much    
greater than is generally imagined4     
,instances might be  mentioned where1 in
 order to keep the common air out of a  
system of  faulty pipes1 a constant     
influx of gas which a pipe two inches in

  diameter can supply has been found    
necessary1 and this of course is just   
so much gas lost to the economy of the  
establishment4    ,with regard to the   
diameter of the mains1 no general rule  
can be given4  ,it must vary according  
to the number of branch pipes and lamps 
which the  main has to supply within a  
given distance1--the angular direction  
of  the mains1--the pressure of the gas 
holder1 and above all1 with the         
relative altitude of the place where the
 gas holder is situated1 and the  place 
at which the gas is to be supplied1 or  
where the lamps are placed4  ,indeed    
this is one of the most important       
considerations with regard to  the      
economical distribution of gas mains1   
and by attending to this  circumstance1 
a prodigious saving may be effected4    
,if the gas flows through a main placed 
at an altitude of the gas holder1  and  
with a pressure to support a column of  
water half an inch high1 this  gas at an
 altitude of #ajj feet1 will support a  

column of water   inch high1 and as the 
velocity of the gas is as the  of the   
height1 or  pressure1 the quantity of   
gas which will flow through a given     
opening at  an elevation of #ajj feet1  
will be very nearly in the proportion of
 two  to three4 ,hence if a gas burner1 
or gas lamp1 produces a flame two       
inches high1 at a place situated on a   
level with the base of the gas  holder1 
the lamp1 if supplied by the same main1 
but situated #ajj feet  higher1 will    
burn with a flame three inches high4    
,this important fact may be rendered    
obvious in the following simple  manner3
    ,take a tube ten or fifteen feet    
long1 and one inch in diameter1 place it
  horizontally2 let one end of the tube 
be open1 and close the other with  a    
plate pierced with a hole1 of about  of 
an inch in diameter1 and  then fill the 
tube with gas4 ,if a lighted taper be   
applied to the hole1  when the tube is  
lying horizontally1 the gas will not    
take fire2 but on  raising the end of   

the tube where the small aperture is1   
the gas will  take fire1 and the        
magnitude of the flame will become      
enlarged in  proportion as the tube     
approaches towards the perpendicular4   
,hence the diameter of gas mains must be
 varied1 according to the  altitude of  
the place to be supplied with gas4 ,and 
it is in consequence  of neglecting this
 principle that we observe so frequently
 certain parts  of large towns scantily 
supplied with gas1 whilst other parts   
furnished  from the same mains1 situated
 considerably above the level of the gas
  holder1 have the gas in the greatest  
profusion1 but at the expense of  those 
places situated at a lower level4 ,and  
so true is this1 that if a  main were to
 descend #ajj feet below the base of the
 gas holder1 and if  the pressure of the
 gas in the main was only equal to      
sustain a column  of water half an inch 
in height1 the gas lamps could not be   
lighted at  all1 at a point so low1     
because the pressure of the gas is then 

in an  equilibrium with the pressure of 
the atmosphere4 ,hence in lighting a    
town or district with coal gas1 the best
 situation for the gas  apparatus1 as   
far at least as it regards the economy  
of the mains for  distributing the gas1 
is the lowest part of the town or       
district4 ,for if  the mains are placed 
at an elevated situation1 they require  
to be  proportionally larger1 and if    
situated at a lower place than the level
  of the gas holder1 they must be       
smaller2 but in either case the mains   
must bear a proper proportion to each   
other1 according to the conditions  and 
circumstances already stated1 and it is 
here1 where the skill of the  gas light 
engineer becomes conspicuous1 for the   
saving that may thus be  effected in the
 lighting of a district or town with    
gas1 is very  considerable4    ,the     
requisite pressure of the gas for       
different situations with regard  to the
 altitude of the place to be lighted1   
may be readily known by  ascertaining   

the altitude of the place by means of   
the mountain  barometer4 ,the           
,englefield mountain barometer is most  
commodious and  suitable for that       
purpose4 ,this instrument is not liable 
to be out of  order1 it may be used by a
 single observer1 and affords an easy   
method  of ascertaining the elevations  
and depressions of the surfaces of the  
earth with the greatest facility1 and to
 a degree of precision1 that may  vie   
with trigonometrical mensuration4 ,thus 
supposing the pressure of the  gas at   
the level of the gas holder to be equal 
to a column of water half  an inch high1
 by inspecting the height of the        
barometer1 the requisite  pressure of   
the gas at that place may readily be    
found4    ,that part of a gas main which
 does not supply any gas to a branch    
pipe  or lamps1 as it proceeds in its   
course need only be a quarter of the    
capacity which is necessary at the part 
where the branch pipe or pipes          
commence4 ,for no inconvenience can     

arise from the increased velocity  which
 the gas must assume in proportion to   
the diminution of the bore  of the main1
 provided that the velocity of the gas  
is lessened by  passing into a main of a
 greater bore1 prior to it being        
conveyed into  the pipe or pipes        
immediately connected with or supplying 
the lamps4 ,the  enlargement of the     
pipes should be in the proportion to the
 diameter of  the two pipes1 as four to 
one4      ,weight of cast iron ,gas     
,mains of different lengths and bores4  
,in order to avoid that the gas mains   
deposited under ground in public        
streets or other places1 may not be on  
the one hand superfluously heavy1  or as
 it is called thick in the metal1 and   
consequently unnecessarily  expensive1  
and on the other hand not too light1 or 
too thin in the  metal1 so as to be     
liable to become injured1 we shall      
exhibit the weight  of gas mains of     
different bores and lengths best suited 
for conveying  gas1 now employed at the 

best regulated gas works in the         
metropolis4#ej      #ej ,a mile of pipe 
of an average diameter1 laid under      
ground ready    for conveying gas1      
together with taking up and making good 
the    pavement1 costs in ,london1 about
 4 #ajjj4--;,and in small towns where   
the lights are usually less clustered   
together than is the case in    ,london1
 and where pipes of three inches in the 
bore are usually    sufficient1 a mile  
of pipe complete costs about 4 #gjj4    
,bore of          ,length      ,weight  
cast iron pipes4   of pipe4     of pipe4
            ,,inches4       ,,feet4     
,,pounds4              #b             #f
            #df              #b         
#f            #fc              #c       
#i           #abj              #d       
#i           #age              #e       
#i           #bdh              #f       
#i           #bhj              #g       
#i           #cfd          ,,part       
,,xiii4      ,gas ,lamps1 and ,burners4 
,the lamps or burners for the combustion

 of coal gas1 may be infinitely  and    
tastefully varied4 ,the varieties       
commonly employed1 are the ,argand      
burner1 the ,cockspur burner1 and the   
,bat's ,wing burner4    ,the ,argand    
burner1 fig4 #aj1 and #aa1 plate ,v41   
consists of two  concentric brass tubes1
 about one and a half inch long1 and    
seven-eighths of an inch in diameter1   
7the largest size burner  employed47    
,the interval between the two tubes is  
closed at top and  bottom4 ,the upper   
part is closed with a ring of steel1 it 
is perforated  with fifteen or eighteen 
holes  of an inch in diameter4 ,the gas 
enters into the cavity between the two  
tubes1 and issues from the  circular row
 of apertures in the steel ring at the  
top of the burner  where it is burnt4 ,a
 double supply of air within and without
 the flame  is effected by means of the 
glass which surrounds the flame4 ,the   
combustion of the gas is perfect when   
the admission of air is in due          
proportion to the magnitude of the      

flame4 ,the height of the gas flame     
should never exceed three times the     
diameter of the flame4 ,when the  flame 
is too large1 the light is less         
brilliant1 and it then produces an      
odour1 because the combustion is        
imperfect4    ,the best shape of the    
glass for surrounding the gas flame of  
the ,argand  lamp1 is a straight tube1  
shown fig4 #h1 plate ,v41 or a tube     
enlarged at  the base1 shown fig4 #i1   
plate ,v4 ,fig4 #aj1 plate ,v41 is      
called a crutched  argand gas burner1 it
 is used for pillar lamps2 fig4 #aa1 is 
called a  branch argand burner4    ,it  
is essential that the apertures for the 
emission of the gas of the  argand gas  
lamp1 be perfectly round and of an      
uniform size1 without this  condition   
the flame of the lamp is ragged1 and not
 well defined4    ,fig4 #ae1 plate      
,,iii41 exhibits a swing bracket1       
furnished with a  cockspur burner4 ,the 
burner consists of a hollow flattened   
globe1  about half an inch in diameter1 

pierced laterally with three or more    
holes1 of about  of an inch in diameter2
 out of these holes the gas  flame      
issues in streams as shown in the       
sketch4 ,with this burner the           
combustion of the gas is imperfect1 and 
it is a wasteful mode of burning  coal  
gas4 ,the surrounding holes of the      
cockspur burner1 was it not for  the    
upward current of air1 would give flames
 radiating in straight lines  from the  
centre of the burner1 but the ascending 
current of heated air1  causes them to  
curve upwards like the spur of a game   
cock1 and hence the  name cockspur      
burner4    ,if the gas be made to burn  
from a series of holes made in the      
lateral  circumference of a hollow flat 
cylinder1 it will produce a circular    
horizontal series of flames curving     
upwards4    ,fig4 #ab4 plate ,v41 is    
called a bat's wing burner2 it consists 
of a  small pear-shaped steel burner1   
about  of an inch in diameter1  having a
 perpendicular slit at its upper        

extremity1 about  of an  inch in        
diameter4 ,this burner exhibits a       
tulip-shaped flame1 as shown  fig4 #ac1 
plate ,v41 it is well adapted for street
 gas lamps4    ,the stop-cock for       
admitting gas into gas burners should   
always be placed  at least six inches   
from the burner4 ,the stop-cock in the  
brackets1 fig4  #h1 or #i1 plate ,v41 is
 placed at a4 ,pendant gas lamps1 into  
which the  gas is conveyed from a pipe  
above1 through the ceiling1 should be   
provided with a mercurial joint1 or ball
 and socket joint4 ,the former          
contrivance is preferable1 because it   
can never leak2#ea but the latter       
requires occasional repairs4 ,fig4 #ad1 
plate ,,iii41 shews the mercurial       
joint4 a1 is the pipe which brings the  
gas2 it terminates in a sheet  iron cup 
open at bottom1 but closed air tight at 
the top2 this cup is  inverted into a   
small iron bason1 containing mercury4 ,d
 the iron tube  which communicates with 
the gas lamp or burner1 and the upper   

extremity  of which projects above the  
surface of the mercury in the iron      
bason1  whilst the other extremity      
proceeds to the burners or lamps4       
#ea ,this contrivance has been adopted  
throughout the fitting up of    the gas 
lights at the ,royal ,mint4    ,swing   
bracket burners1 fig4 #ac1 plate ,,iii41
 should have the axis of  motion at the 
joints ,a1 ,a1 ,a1 perforated at right  
angles to each other1  so as to admit   
the moveable joints at ,a1 to be left   
open1 without  obstructing the passage  
of the gas when the bracket assumes     
different  angular positions4 ,all swing
 brackets ought to have a double1 and   
not a  single joint1 because the latter 
soon wears oval in the two opposite     
edges2 this is prevented by the double  
joint having an uniform bearing  at top 
and bottom1 it therefore can never leak4
    ,fig4 #aa1 plate ,,vi41 exhibits the
 arrangement usually adopted for a      
pendant perpendicular sliding lamp1 or  
chandelier1 which requires to  be raised

 or depressed4 ,this contrivance is     
convenient for lighting  theatres1 or   
public buildings1 by means of a large   
central gas light  chandelier1 that may 
be raised or depressed at pleasure4     
,the gas enters into the tube ,d1 which 
is firmly fixed in the ceiling1  as     
shown in the sketch2 it passes through a
 hole near ,e1 into a smaller  tube j1  
which slides perpendicularly within the 
tube ,d4 ,this sliding  tube is made air
 tight by means of two stuffing boxes   
filled with oil1  placed near ,b1 and   
,c4 ,the sliding tube j1 together with  
the chandelier  suspended to it1 is     
counter-balanced by a weight concealed  
in a box ,w1  connected with pullies in 
the usual manner1 as shown in the       
sketch1 so  that the chandelier may be  
raised or lowered at pleasure4          
,directions to ,workmen1 for adapting   
,gas ,pipes to the interior of  houses4 
,the adapting gas pipes to the interior 
of houses1 for the supply of gas1       
simple and easy as it may appear1 has   

been the means of not a little          
contributing to bring the gas light     
illumination1 on many occasions1  into  
disrepute4 ,it has required years to    
enable workmen of the best  intention to
 acquire sufficient practical skill in  
the proper execution  of a business1    
which must be pronounced to constitute  
an art entirely  new1 and in which no   
progress could be made1 but after having
 committed  many errors4 ,a house neatly
 and judiciously fitted up with gas     
pipes1  displays to a person experienced
 in this art1 a skill and judgment1     
equal to what is established in any     
other branch of mechanical  employment4 
,it must be obvious1 that the art of    
arranging the pipes and  adapting them1 
is one of that class of operations in   
which it is a real  saving to employ the
 best materials and skilful workmen1 to 
avoid  repairs and subsequent           
alterations and derangements of the     
work4 ,the  supply and distribution of  
the pipes1 or the fitting up1 as it is  

called by the workmen1 may be done      
almost at any price with regard to      
workmanship and materials1 and to       
bargain for cheapness in the execution  
of it1 with a faithful1 honest1 and     
skilful workman1 must naturally be a    
losing concern to the person for whom   
the work is done4 ,the cost of          
furnishing and adapting the pipes to one
 place1 cannot serve as a  standard for 
any other place1 every separate place   
may present  difficulties which could   
not be foreseen at the commencement of  
the  work4    ,the stopping up and      
corrosion of the gas pipes1 which at the
  commencement of the introduction of   
the new lights was complained of in     
many places1 it is now sufficiently     
established1 originated entirely  from  
the impurity of the gas1 together with a
 faulty arrangement of the  pipes1 in   
consequence of which1 the water of      
condensation accumulating  in certain   
parts1 exercised a strong chemical      
action on the copper  pipes1 and if the 

gas was not very pure1 ultimately       
corroded the pipe4  ,these objections do
 no longer exist1 and it may safely be  
pronounced1  that pure coal gas produces
 no action whatever on the copper tubes 
through which it is conveyed4 ,in proof 
of this statement1 we need only  refer  
to the several districts of the         
metropolis1 fitted up with gas  pipes at
 the first introduction of the new      
lights1 7#ahji17 all of which  are still
 in perfect preservation4    ,it is     
perhaps unnecessary to add1 that no pipe
 capable of being melted  by a gas      
flame1 should ever be employed for      
conveying or distributing  gas through  
the interior of houses1 because the     
facility with which such  pipes might be
 perforated1 could lead to serious      
consequences1 if the  gas issuing from  
the aperture of the pipe were lighted1  
the flame in  that case would follow the
 melted part1 through the whole extent  
of the  pipe1 and the hazard by fire    
would be considerably increased4        

,therefore1 pewter1 lead1 and tin pipes1
 are very improper for  distributing gas
 through the interior of houses1 and    
should never be  used for that purpose4 
,hence copper1 and iron pipes1 are      
universally  employed4    ,in order that
 the pipes for conveying the gas from   
the mains1 and  distributing it through 
the houses or other buildings to be     
lighted with  gas1 may in the first     
place not be unnecessarily large1 or too
 small1  the following rule may serve as
 a guide to workmen3    ,one gas        
lamp1--consuming four cubic feet of gas 
in an hour1 if situated  twenty feet    
distance from the main which supplies   
the gas1 requires a  tube not less than 
a quarter of an inch in the bore4       
,two lamps1--#cj feet distance from the 
main1 require a tube  of an  inch in the
 bore4    ,three lamps1--#cj feet       
distance from the main1 require a tube  
of an  inch in the bore4    ,four       
lamps1--#dj feet distance from the main1
 require a tube  inch in  the bore4     

,six lamps1--#ej feet distance from the 
main1 require a tube  of an  inch in the
 bore4    ,ten lamps1--#ajj feet        
distance from the main1 require a tube  
of an  inch in the bore4    ,fifteen    
lamps1--#acj feet distance from the     
main1 require a tube #a inch  in the    
bore4    ,twenty lamps1--#aej feet      
distance from the main1 require a tube  
#a inch  in the bore4    ,twenty-five   
lamps1--#ahj feet distance from the     
main1 require a tube #a  of an inch in  
the bore4    ,thirty lamps1--#bjj feet  
distance from the main1 require a tube  
#a inch  in the bore4    ,thirty-five   
lamps1--#bej feet distance from the     
main1 require a tube #a  of an inch in  
the bore4    ,all copper pipes employed 
to convey gas through the interior of   
houses  should be of the following      
weight1 with regard to a given length of
 the  pipe3      ,bore of the pipe4     
,weight per foot4     ,,parts ,,of ,,an 
,,inch4           ,,ounces4             
#c                                 #e   

#f                                 #h   
#aj    ,no coppered pipes should be used
 but such as have wrapt over and brazed 
joints4 ,they should be well annealed1  
to render them pliable without  being   
liable to break4    ,all the bends for  
connecting pipes must be circular1 see  
fig4 #bb1 plate  ,v4    ,no branch pipe 
ought to proceed from a pipe of a       
quarter of an inch in  the bore1 and no 
more than two branch pipes should       
proceed from a pipe  three-eighths of an
 inch in the bore4    ,all branch pipes 
before they are fixed for conveying gas1
 must be proved  by condensing air into 
them by means of a condensing hand pump4
 ,the pipe  should be placed in a trough
 of water1 the leak will then be easily 
observed by the air bubbles which rise  
through the water whilst the air  is    
condensed in the pipes4    ,all branch  
pipes should have a rectilinear course2 
pipes that are  twisted have an         
unsightly appearance4    ,all pipes     
should have a descent of no less than a 

quarter of an inch in  four feet4       
,the seams or brazed part of the pipes  
must always be out most and not  towards
 the wall2 because if a leak should     
happen to take place in the  brazed part
 of the pipe1 it may then be easily     
discovered and more  readily repaired4  
,when all the pipes have been furnished 
to a house or place intended to  be     
lighted1 the whole system of the pipes  
should be examined with the  utmost     
rigour1 to ascertain whether all the    
junctures are air tight4  ,this should  
be done by condensing air into the pipes
 by means of a  condensing syringe1 and 
if the piston of the syringe lowers     
after  condensation1 it is a sure       
indication that the pipes are faulty1   
and  consequently totally unfit for     
receiving the gas4 ,the leak may be     
detected by passing a lighted taper     
carefully along the whole extent of  the
 pipe filled with condensed air1 when   
the flame of the taper will be  affected
 as it passes over the faulty place of  

the pipe4    ,the aperture from which   
the gas can escape may however1 be so   
small1 as  to render it a matter of     
difficulty to discover it in the manner 
just  stated2 but when the pipes are    
filled with coal gas1 the escape of it1 
when all the stop-cocks of the lamps and
 burners are shut1 will soon  become    
obvious1 by the peculiar odour of the   
gas1 if the apartment1 or  place1 where 
the pipes are placed1 is suffered to be 
closed for about  twenty-four hours4    
,the gas should not be introduced into  
pipes in which  any defect of this kind 
is found1 until it be completely        
removed4 ,the  most severe trial to     
ascertain the air tightness of any      
system of pipes  is1 the trial by       
exhaustion1 by means of an air pump1 for
 the guage of  the pump will discover   
the minutest leak1 which the preceding  
method of  proving pipes can not        
discover4    ,all pipes after being     
proved should be painted of the same    
colour as the  surface to which they are

 affixed4    ,the whole system of pipes 
should incline to one or more places1 so
 that  any moisture that may happen to  
accumulate in the pipes1 may collect at 
such places1 whence it may be readily   
removed by opening a screw plug  adapted
 for that purpose4    ,all the different
 junctures of mains and branch pipes1   
should be  effected by means of         
connecting pieces1 so that any part of  
the system  of the pipes1 or any        
separate branch pipe may readily be     
detached1 and  put up again if occasion 
should require it2 fig4 #ai1 plate ,v41 
exhibits  this mode of connecting gas   
pipes by means of union joints4 ,a1 ,b1 
,c1 ,d1  ,e1 shows a gas pipe with its  
union or connecting joint1 divided into 
its  separate parts4 ,d1 is a collar of 
leather1 which passes over the part  ,c1
 of the union joint1 close up to the    
shoulder of the joint2 the  opposite    
extremity of the pipe may be inserted   
into the socket ,b1 so  that the        
shoulder ,c1 comes in contact with the  

fillet or rim in ,b1 to  prevent it     
passing over the shoulder ,c1 when ,b   
and ,e are screwed  together4 ,the      
latter part of the pipe is furnished    
with a male screw to  correspond with   
the thread in the collar ,b4 ,the       
shoulder piece ,c1 is of  rather a      
larger diameter than the bore of the    
tube ,a1 with which it is  to be        
connected4 ,the short piece ,e1         
furnished with a male screw1 is of  the 
same diameter as the part ,c4 ,the      
pieces ,c1 and ,e1 of the pipe are  soft
 soldered1 one to the tube ,a1 and the  
other to the tube ,e1 but  previous to  
soldering on ,c1 it is necessary that   
the socket should be  inserted into the 
tube ,a1 it will then be ready for      
connecting1 as will  become obvious by  
inspecting fig4 #bj1 which shows the    
various parts of  the union joint fitted
 for use4 ,it is evident that if the    
extremity ,d1  in the pipe ,b1 be       
brought close to the pipe ,e1 and if the
 socket ,c1 be  moved along the pipe ,a1

 and screwed upon the male screw at ,d1 
as far as  it will go1 the face of the  
part ,d1 must press close against the   
leather  collar which is placed on ,e1  
and render the joint gas tight4 ,these  
kind  of joints are very convenient for 
circular bends1 fig4 #bb1 and ,t1       
pieces1 fig4 #ba4 ,the ,t pieces1 fig4  
#ba1 are very useful for collateral     
branch pipes1 either for the same or of 
a less diameter as the pipe1  from which
 they proceed1 so as to branch off at   
right angles4    ,fig4 #bb1 is a quarter
 circular bend2 it is convenient for    
adapting tubes  along the angular parts 
of rooms1 and to all such situations    
where the  tube is to have a sudden     
circular course4 ,small copper tubes may
 be  readily bent to the required angle 
without breaking1 but if a tube  should 
terminate in any angular part of a room1
 in that case a circular  bend furnished
 with a male and female screw1 is       
convenient for  connecting the pipes    
together4    ,all pipes adapted to the  

exterior of buildings1 should be kept a 
little  distance off from the wall1 to  
prevent the wet lodging between the pipe
  and the surface to which they adapted4
    ,sheet iron mains for the interior  
of houses1 are preferable to copper     
mains1 provided the course of the main  
with regard to the position of  the     
branch pipes1 does not require too many 
angular directions1 or  circular bends4 
,,part ,,xiv4      ,illuminating power  
of ,coal ,gas1 and quantity of ,gas     
consumed in a given  time1 by different 
kinds of ,burners1 and ,gas ,lamps4     
,the illuminating power of coal gas1    
differs according to the nature of  the 
coal from which it is obtained1 and the 
manner in which it is  purified1        
together with the quantity of naptha or 
essential oil  chemically combined1 or  
mechanically suspended in the gas4 ,for 
if the  gas be strongly agitated with   
water1 its illuminating power is        
diminished4 ,coal gas1 which abounds in 
olifiant gas or supercarburetted        

hydrogen possesses the greatest         
illuminating power1 and hence           
carburetted hydrogen obtained from the  
decomposition of coal tar  possesses a  
greater illuminating power than the gas 
obtained from the  coals which produced 
the tar4 ,the illuminating power of     
carburetted  hydrogen obtained from coal
 tar when compared to the gas obtained  
from  the best ,newcastle coal is in the
 proportion as six to five4 ,in fact the
  intensity of light evolved during the 
combustion of gazeous bodies  composed  
of carbon1 hydrogen1 and oxigen1 is     
always in the ratio of the  quantity of 
carbon contained in equal quantities of 
the gazeous  compound1 and hence the gas
 from animal oil which is chiefly       
composed of  supercarburetted hydrogen  
or olifiant gas1 surpasses in           
illuminating  power the gas obtained    
from coal4    ,half a cubic foot of coal
 gas1 obtained in the ordinary way of   
manufacturing coal gas1 from ,newcastle 
coal1 is equal in illuminating  power   

and duration of time1 to the light      
produced by a tallow candle six  in the 
pound1 burning for one hour1 and as such
 a tallow candle lasts  five hours1     
therefore fifteen cubic feet of coal    
gas1 are equal in value  with regard to 
illuminating power to one pound of      
candles4 ,and as #aab  pounds of        
,newcastle coal produce by the new      
method of manufacturing coal  gas1 at   
least #eej cubic feet of gas1 therefore 
the quantity of gas  produced from a    
chaldron of ,newcastle or ,sunderland   
coal1 7the minimum  weight of which is  
#bg cwt47 is equal in illuminating power
 to #ajjj  pounds of tallow candles4    
,the illuminating power of coal gas may 
readily be ascertained4 ,though  the eye
 is not fitted to judge of the          
proportional power of different  lights1
 it can distinguish in many cases with  
sufficient precision where  two similar 
surfaces are equally illuminated4 ,as   
the lucid particles  emitted from       
luminous bodies are darted in right     

lines1 they must spread  uniformly1 and 
hence their density diminishes in the   
duplicate ratio of  their distance4     
,from the respective situations1        
therefore1 of the  centres of           
divergency1 when the contrasted and     
illuminated surfaces  become equally    
bright1 we are enabled to compute their 
relative degrees  of intensity4 ,and for
 this purpose it is assumed as a        
principle1 that  the same quantity of   
light1 diverging in all directions from 
a luminous  body1 remains undiminished  
in all distances from the centre of     
divergency4    ,thus we must suppose1   
that the quantity of light falling on   
every  object1 is the same as would have
 fallen on the places occupied by the   
shadow2 and if there were any doubt of  
the truth of the supposition1 it  might 
be confirmed by some simple experiment4 
,therefore1 it follows1 that1 since the 
shadow of a square inch of any  surface 
occupies at twice the distance of the   
surface from the luminous  point the    

space of four square inches1 the        
intensity of the light  diminishes as   
the square of the distance increases4   
,if1 consequently1 we  remove the two   
sources of light to such distances from 
an object that  they may illuminate it  
in equal degrees1 we are authorized to  
conclude  that their original           
intensities are inversely as the squares
 of the  distances4    ,hence1 if two   
lights of unequal illuminating powers   
shine upon the same  surface at equal   
obliquities1 and an opaque body be      
interposed between  them and the        
illuminated surface1 the two shadows    
produced must differ  in blackness or   
intensity in the same degree4 ,for the  
shadow formed by  intercepting the      
greater light1 will be illuminated by   
the smaller light  only2 and reversely1 
the other shadow will be illuminated by 
the greater  light2 that is to say1 the 
stronger light will be attended with the
  deeper shadow4    ,now it is easy by  
removing the stronger light to a greater

 distance1 to  make the shadow which it 
produces equal to that afforded by the  
less  light4 ,experiments of this kind  
may be made in the following manner3    
,fasten a sheet of white paper against  
the wall of a room1 and place the  two  
lights intended to be compared1 so that 
the rays of light from each  fall with  
nearly the same angle of incidence upon 
the middle of the  paper4 ,in this      
situation1 if a book or other object be 
held to intercept  part of the light1   
which would have fallen on the paper1   
the shadows may  be made to appear as in
 this figure3    ,illustration    where 
,a represents the surface illuminated by
 one of the lights  only2 ,b1 the       
surface illuminated by the other light2 
,c1 the perfect  shadow from which both 
lights are excluded4 ,it will easily be 
understood  that the lights about ,d and
 ,e1 near the angle ,f1 will fall with  
equal  incidences when the double shadow
 is made to occupy the middle of the    
paper2 and consequently1 if one or both 

of the lights be removed  directly      
towards or from the paper1 as the       
appearances may require1  until the two 
shadows at ,e and ,d have the same      
intensity1 the quantities  of light     
emitted by each1 will be as the squares 
of the distances from  the paper4    ,by
 experiments of this kind1 many useful  
particulars may be shewn2 for1  since   
the cost and duration of candles1 and   
the consumption of coal gas1  or oil in 
lamps1 are easily ascertainable1 it may 
be shewn whether more  or less light is 
obtained at the same expense during a   
given time1 by  burning a number of     
small lights1 instead of one or more of 
greater  intensities4 ,and thus we may  
compare the power of different kinds of 
lamps or candles1 with gas lights of    
different intensities1 so as to         
determine the relative cost of each     
particular kind of the combustible      
substance employed for furnishing light4
 ,for example2 if a candle and a  gas   
burner supplying coal gas1 adjusted by a

 stop-cock1 produce the same  darkness  
of shadow1 at the same distance from the
 wall1 the strength or  intensity of    
light is the same4    ,an uniform degree
 of intensity of the gas light may      
readily be  produced1 by opening or     
shutting the stop-cock1 if more or less 
light be  required1 and the candle kept 
carefully snuffed to produce the most   
regular and greatest quantity of light4 
,the size of the flame1 in  experiments 
of this kind1 of course becomes         
unnecessary1 and will vary  very much   
with the quality or chemical            
constitution of the coal gas4 ,the  bulk
 of the gas consumed1 and the weight of 
tallow or oil used by  weighing the     
candle or oil before and after the      
experiment furnish the  data for        
calculating the relative cost of tallow1
 or oil and gas1 when  compared with    
each other4    ,the following statement 
exhibits the quantity of coal gas       
consumed in a  given time1 by different 
kinds of argand lamps4 ,an argand burner

 which  measures in the upper rim half  
an inch in diameter1 between the holes  
from which the gas issues1 when         
furnished with five apertures #e part   
of an inch in diameter1 consumes two    
cubic feet of gas in an hour1 when  the 
gas flame is one and a half inch high4  
,the illuminating power  produced by    
this burner is equal to three tallow    
candles eight in the  pound4    ,an     
argand burner three quarters of an inch 
in diameter between the  holes in the   
upper rim1 and perforated with holes1   
of an inch in  diameter1 consumes three 
cubic feet of gas in an hour1 when the  
flame is  two and a quarter inches high1
 and produces a light equal in intensity
  to four tallow candles1 eight in a    
pound4    ,an argand burner             
seven-eighths of an inch in diameter1   
perforated with  eighteen holes  of an  
inch in diameter1 consumes when the     
flame of  the gas is three inches high1 
four cubic feet of gas in an hour1 and  
produces a light equal in intensity to  

six tallow candles1 eight in the  pound4
    ,when the flame obtained by these   
kind of burners rises to a greater      
height1 than what has been stated1 the  
combustion of the gas is  imperfect1 the
 intensity of the light becomes         
diminished1 and there is a  waste of    
gas4 ,the same holds good with regard to
 the size of the holes  from which the  
gas issues2 if the holes be made larger 
than #e part of  an inch in these kind  
of burners1 the gas is not completely   
burnt1 and  its illuminating power      
decreases4    ,the height of the glass  
which surrounds the flame1 should never 
be less  than five inches1 and the      
interval for the current of air within  
and  without the flame1 ought to bear   
the usual proportion adopted for the    
combustion of oil in the common argand  
lamps of similar diameters4             
,ventilation of ,apartments lighted by  
,coal ,gas4    ,before means had been   
devised for the effectual purification  
of coal  gas1 a disagreeable odour was  

found to attend its combustion in an    
impure state1 and hence an opinion      
became prevalent1 that the benefit of   
this new species of illumination must be
 confined to open places1 and  that it  
could not with any regard to pleasure or
 salubrity1 be adapted  to private      
dwellings4    ,the art of purifying coal
 gas1 has at length however1 been       
carried to  such a perfection1 that     
every possibility of a disagreeable     
odour  arising from its combustion has  
been wholly removed1 in all cases where 
attention is paid to the perfect        
combustion of the gas1 by keeping the   
flame of the same of a proper magnitude4
    ,and since this improvement1 the use
 of coal gas1 as a means of             
illumination has become as general1 and 
has been found attended with as         
superior advantages within doors as     
without1 and hence a vast number of     
dwelling houses are now lighted         
throughout with gas4    ,although there 
is no occasion therefore1 to make       

provision for  ventilating apartments   
where gas light is employed1 on account 
of any  odour which it can produce when 
honestly used1 so that the combustion is
  perfect1 yet on other accounts such   
means of ventilations are very  salutary
 and necessary4    ,the flame of coal   
gas produces a degree of heat1#eb which 
in some  places1 such as large public   
offices1 and warehouses of dry goods1 is
 a  strong additional recommendation in 
favour of its use1 7page #ae17 while  in
 others1 on the contrary1 such as small 
rooms numerously frequented1  and shops 
containing commodities requiring to be  
kept cool1 it can only  be used         
beneficially when means are provided for
 conveying away the  heated air4        
#eb ,mr4 ,dalton's method of            
ascertaining the comparative effect of  
heat evolved during the combustion of   
inflammable gases1 and other            
substances capable of burning with      
flame1 7,dalton's ,system of            
,chemistry1 vol4 ,i4 p4 #gf17 is simple1

 easy1 and accurate4 ,it is as          
follows3      ,take a bladder of any    
size1 7let us suppose for the sake of   
illustration1 the bladder to hold       
#cj1jjj grains of water17 and having    
furnished it with a stop-cock and small 
jet pipe1 fill it with the              
combustible gas the heating power of    
which is to be tried4 ,take also a      
tinned iron vessel with a concave bottom
 of the same capacity1 pour    into it  
as much water as will make the vessel   
and water together equal    to the bulk 
of the water in the bladder1 viz4       
#cj1jjj grains4 ,then set    fire to the
 gas at the orifice of the pipe1 bring  
the point of the    flame under the     
bottom of the tinned vessel1 and suffer 
it to burn    there1 by squeezing the   
bladder till the whole of the gas is    
consumed4    ,the increase of           
temperature of the water in the tinned  
vessel before    and after the          
experiment1 expresses very accurately   
the heating power    of the given bulk  

of the inflammable gas4 ,it was thus    
proved that--      ,olifiant gas raises 
an equal volume of water #ad deg4       
,carburetted hydrogen1 or coal gas      
#aj    ,carbonic oxid gas               
#d    ,hydrogen gas                     
#e    ,spermaceti oil1 #aj grains burnt 
in a lamp      raised #cj1jjj grains of 
water               #e    ,tallow       
#e    ,wax                              
#e1ge    ,oil of turpentine             
#c    ,spirit of wine                   
#b      ,the best method for this       
purpose is to make an aperture of about 
two or  three inches in diameter into   
the chimney near the ceiling1 and       
inserting into it a tube bending upwards
 into the interior of the  chimney4 ,a  
complete ventilation of the room will   
thus be established1 by  producing an   
extra vent which will be amply          
sufficient for carrying off  the heated 
air4 ,the aperture can easily be masked 
with some ornamental  open work1        
corresponding with the style of the     

room4    ,if there happens to be no     
chimney in the apartment1 the ventilator
 may  be made in the ceiling1 and the   
tube may be carried between the ceiling 
and the floor above1 into the open air4 
,the mode of ventilation now  suggested1
 has been uniformly found most          
efficient1 and has1 under  existing     
circumstances1 a decided superiority    
over another method1 which  we see in   
some instances adopted4 ,this method    
consists in enclosing the  gas burner in
 a bell-shaped glass1 from the upper    
part of which a large  copper tube      
proceeds1 and leads out into the open   
air4 ,it is certain  that by this means 
not only the heated air is carried off1 
and the  possibility of any waste gas   
escaping into the apartment is also     
completely prevented4 ,but at the same  
time1 by taking away all occasion  for a
 prudent limitation in the use of the   
gas1 it exposes it to a  degree of      
improvident waste1 in the hands of      
dishonest and careless  individuals1    

which must prove ruinous to the         
manufacturer4 ,the mode of  regulating  
the light of the flames by means of the 
governor1 of which a  description has   
been given1 page #bcb1 indeed provides a
 check against  such waste1 and there   
can be no doubt that in proportion as   
this  instrument gets into general use1 
the objection on this score must of     
course fall to the ground2 but under any
 circumstances the inelegance of  the   
contrivance of such an object in a      
chamber1 as the large branching  tube1  
must always induce a preference1 for the
 more simple1 and for all  necessary    
purposes1 equally efficient method1 of  
the ventilator before  described4       
,,part ,,xv4      ,gas from ,coal ,tar4 
,although the tar which forms one of the
 products obtained from the             
decomposition of pit coal1 in the       
manufacture of coal gas1 has become an  
article of commerce1 being found        
applicable to most of those purposes to 
which vegetable tar has hitherto been   

used1 it appears from experiments  made 
on a large scale1 that instead of thus  
disposing of the coal tar1  it is more  
profitable1 under certain circumstances1
 to submit this  substance to a         
destructive distillation1 for the       
purpose of obtaining  from it           
carburetted hydrogen gas1 which it is   
capable of affording1 not  only in      
abundance1 but of a superior quality4   
,the chief circumstances which must     
determine the manufacturer of coal  gas 
in this respect1 is the price at which  
he can sell the coke produced  in his   
establishment4 ,if the price of this    
article is high1 if he finds  a ready   
market for coke1 there is every reason  
to believe1 that the  manufacturer will 
find it more to his advantage to dispose
 of the tar1  and to manufacture gas    
from coal alone1 in order to increase   
his store  of coke4 ,but if coke happens
 to be at a low price1 and not          
disposable  with advantage1 the         
manufacturer will do well to make the   

coal go as far  as possible in the      
production of gas1 and under such       
circumstances he  will keep and convert 
the tar into gas1 thus consuming less   
coal and  having less of the burdensome 
article1 coke1 to dispose of4    ,the   
profit however1 to be gained from the   
sale of coke1 must be both  certain and 
considerable1 to induce a preference for
 the former course2  because the        
decomposition of coal tar1 besides      
superseding a  proportionate quantity of
 coal1 is attended with several other   
very  tempting advantages4    ,from     
experiments lately made in the          
metropolis on this subject1 in which  ,i
 have been engaged1 it appears that in  
all large gas light  establishments1    
where the quantity of coal tar rapidly  
accumulates1 and  must be got rid of1   
and in all places where the tar cannot  
be sold for  more than four shillings   
the hundred weight1 it will be certainly
  advantageous to the manufacturer to   
decompose the tar for the production  of

 carburetted hydrogen gas4    ,the price
 of coal cannot effect the operation1   
because where coal bears  a high price1 
the manufacturer of the tar gas1 will   
diminish the  quantity of coal which he 
would otherwise be called upon to employ
 for  the production of the requisite   
quantity of gas4 ,and in places where   
coal is cheap1 the decomposition of the 
tar will be attended with less  expence4
    ,the carburetted hydrogen gas       
produced from coal tar1 possesses a     
greater  illuminating power than the gas
 obtained from coal4#ec ,it consists    
chiefly of supercarburetted hydrogen or 
olifiant gas1 and a less  quantity of it
 is of course sufficient4      #ec      
,vegetable tar1 also affords carburetted
 hydrogen gas in    abundance1 and this 
no doubt might be employed to great     
advantage for    the production of      
artificial light in places where it is  
cheap4 #bab    pounds of the most viscid
 ,swedish tar1 produce #adhd cubic feet 
of    carburetted hydrogen1 7or seven   

cubic feet to one pound of tar17 the    
illuminating power of this gas is equal 
to the gas obtained from pit    coal4   
,the gas thus obtained1 is purified     
likewise with far greater facility1     
taking only one hundred and twentieth   
part of the quantity of quicklime  which
 is required for the purification of    
carburetted hydrogen obtained  from pit 
coal4 ,the apparatus for the production 
of carburetted hydrogen  from coal tar1 
is moreover less bulky1 less expensive1 
and less  complicated2 and it can be    
managed by fewer workmen4 ,and as the   
combined  result of these several       
advantages1 it is obvious1 that by the  
substitution of coal tar1 the new mode  
of lighting by gas can be pursued  on a 
smaller scale2 which it can never be    
with any profit1 where coal  itself is  
immediately employed for the production 
of the gas4    ,the apparatus employed  
by ,mr4 ,clegg1 for the distillation of 
tar1 is  extremely simple4 ,it consists 
of two hollow cast iron cylinders1      

twelve  inches in diameter1 and nine    
feet long1 furnished with moveable lids 
or  mouth pieces1 and joined together at
 the extremity opposite to the mouth    
piece4 ,these cylinders are fixed in a  
brick furnace1 so that each  inclines   
eleven degrees1 one above and the other 
below the horizontal  base of the       
furnace4    ,when the apparatus has     
acquired a dull red heat1 the coal tar  
is  suffered to flow into the upper     
cylinder1 by small portions at a time4  
,the tar is contained in a closed       
vessel1 situated at any convenient      
place above the apparatus4 ,it has a    
small aperture for the admission of     
air4 ,but as a sufficient small quantity
 of viscid tar does not flow  freely in 
a thin stream1 a larger portion than is 
wanted1 is made to  flow first into a a 
small box1 upon the apex of a pyramid   
which divides  the stream1 so that the  
excess runs off by a waste pipe1 whilst 
a due  quantity only is conveyed into   
the retort where it is decomposed4      

,this apparatus#ed therefore differs    
only from the apparatus described  in   
the ,journal of ,science and the ,arts1 
#ahaf1 ,no4 ,,ii41 p4 #bhb2 that the    
cylinders may be detached1 for cleaning 
them out more conveniently4      #ed    
,now erecting at ,birmingham4    ,the   
following statement exhibits the result 
of a series of experiments1  made       
7#ahaf17 at the ,westminster ,chartered 
,gas ,light ,establishment1#ee  for the 
purpose of ascertaining how far1 and    
under what circumstances  the           
decomposition of coal tar is a measure  
of economy4      #ee ,communicated by   
,mr4 ,t4 ,s4 ,peckston4      ,two tar   
retorts worked seven hours1 produced    
#cjed cubic feet of gas4    ,the        
quantity of tar decomposed1 amounted to 
#ced lb4 therefore #h cubic    feet of  
gas1 7omitting fractions71 were obtained
 from #a lb4 of tar4      ,two tar      
retorts1 worked nine hours1 produced    
#deia cubic feet of gas4    ,the        
quantity of tar decomposed1 was #ebe lb4

 ,hence #a lb4 of tar yielded    nearly 
#h cubic feet of gas4      ,fifteen cwt4
 #af lb4 of tar1 produced #af1aab cubic 
feet of gas1  #i    cubic feet of gas1  
to #a lb4 of tar4      ,five cwt4 #c    
quarters1 #bb lb4 of tar1 produced #fffj
 cubic feet of gas1     #aj cubic feet  
of gas to #a lb4 of tar4      ,five cwt4
 #ag lb4 of tar1 produced #eaic cubic   
feet of gas1  #i cubic    feet of gas to
 #a lb4 of tar4      ,one cwt4 #ha lb4  
of tar1 produced #agcg cubic feet of    
gas1  #i cubic    feet of gas to #a lb4 
of tar4      ,one cwt4 #cj lb4 of tar1  
produced #acac cubic feet of gas1  #h   
cubic    feet of gas to #a lb4 of tar4  
,five cwt4 of tar1 produced #ehhj cubic 
feet of gas1  #aj cubic feet    of gas  
to #a lb4 of tar4      ,two cwt4 of tar1
 produced #bjgb cubic feet of gas1  #i  
cubic feet of    gas to #a lb4 of tar4  
,three cwt4 #ah lb4 of tar1 produced    
#cgag cubic feet of gas1  #aj    cubic  
feet of gas to #a lb4 of tar4      ,two 
cwt4 #f lb4 of tar1 produced #bbdb cubic

 feet of gas1  #i    cubic feet of gas  
to #a lb4 of tar4    ,from the preceding
 operations it becomes obvious1 that #i 
cubic feet  of gas1 were obtained in the
 large way from #a lb4 of tar4 ,but this
  proportion appears evidently too      
small1 our own operations assign        
fifteen cubic feet of gas to one pound  
of tar4 ,professor ,brande1  obtained   
eighteen cubic feet#ef from the same    
quantity of tar4      #ef ,journal of   
,science and the ,arts1 #ahaf1 ,no4     
,,ii4 p4 #bhb4      ,gas from ,oil4     
8,messrs4 ,j4 and ,p4 ,taylor#eg are the
 first persons who have resorted to  oil
 as a substance from which gas for      
illumination could be easily and        
cheaply prepared2 and in the            
construction of a convenient apparatus  
for  the decomposition of this body1    
they have fully shewn its numerous      
advantages over coal1 while they have   
afforded the means of producing  the    
most pure and brilliant flame from the  
inferior and cheap oils1  which could   

not be used in lamps4 ,the apparatus for
 the purpose is much  smaller1 much     
simpler1 and yet equally effectual1 with
 the best coal gas  apparatus4 ,the     
retort is a bent cast iron tube1 which  
is heated red by a  small convenient    
furnace1 and into which oil is allowed  
to drop by a  very ingenious apparatus2 
the oil is immediately volatilized1 and 
the  vapour in traversing the tube      
becomes perfectly decomposed4 ,a mixture
 of  inflammable gases1 which contains a
 great proportion of olifiant gas       
passes off2 it is washed by being passed
 through a vessel of water  7which      
dissolves a little sebacic acid1 and    
which seldom requires  changing71 and is
 then conducted into the gasometer40    
#eg ,copied from the ,journal of        
,science and the ,arts1 ,vol4 ,,vi4 p4  
#ajh4    8,the facility and cleanliness 
with which gas is prepared from oil in  
the  above manner1 may be conceived from
 the description of the process4 ,a     
small furnace is lighted1 and a         

sufficient quantity of the commonest oil
  is put into a small iron vessel1 a    
cock is turned1 and the gas after       
passing through water in the washing    
vessel1 goes into the gasometer4  ,the  
operation may be stopped by shutting off
 the oil1 or1 to a certain  extent1     
hastened by letting it on more freely2  
the small quantity of  charcoal         
deposited in the retort is drawn out by 
a small rake1 and the  water of the     
washer is very rarely changed40    8,the
 gas prepared from oil is very superior 
in quality to that from  coal2 it cannot
 possibly contain sulphuretted hydrogen1
 or any  extraneous substance2 it gives 
a much brighter and denser flame2 and it
  is also more effectual1 i4 e4 a lesser
 quantity will supply the burner  with  
fuel4 ,these peculiarities are          
occasioned1 in the first place1 by  the 
absence of sulphur from oil1 and then by
 the gas containing more  carbon in     
solution4 ,as the proportion of light   
given out by the flame of  a gaseous    

compound of carbon and hydrogen1 is in  
common circumstances in  proportion to  
the quantity of carbon present2 it is   
evident that the gas  which contains a  
greater proportion of olifiant gas1 or  
supercarburetted  hydrogen than coal    
gas1 will yield a better and brighter   
light on  combustion40    8,it is       
necessary1 in consequence of the        
abundance of charcoal in  solution1 to  
supply the gas when burning with plenty 
of atmospheric air1  for as there is    
more combustible matter in a certain    
volume of it1 than  in an equal volume  
of coal gas1 it of necessity must have  
more oxigen  for its consumption4#eh    
,the consequence is1 that less gas must 
be burnt  in a flame of equal size1     
which will still possess superior       
brilliancy2  that less is necessary for 
the same purpose of illumination2 and   
that  less heat will be occasioned4     
,from five and a half to six cubical    
feet  of coal gas are required to supply
 an ,argand burner for an hour2 two     

cubical feet to two and a half of that  
from oil1 are abundantly  sufficient for
 the same purpose40      #eh ,dr4 ,w4   
,henry's experiments gave the following 
result3--#ajj cubic    inches of        
carburetted hydrogen from coal1 require1
 for burning1 #bbj    cubic inches of   
oxigen1 and produce #ajj cubic inches of
 carbonic    acid--#ajj cubic inches of 
carburetted hydrogen gas procured from  
lamp    oil1 require #aij cubic inches  
of oxigen1 and produce #abd cubic inches
    of carbonic acid1--#ajj cubic inches
 of carburetted hydrogen obtained       
from wax1 require #bhj cubic inches of  
oxigen1 and produce #acg cubic    inches
 of carbonic acid4    8,one important   
advantage gained by the circumstance1   
that so small a  quantity of this gas is
 necessary for burners is1 that the     
gasometer  required may be small in     
proportion4 ,the gasometer is the most  
bulky  part of a gas apparatus1 and that
 least capable of concentration2 and    
where-ever it is placed1 it occupies    

room to the exclusion of every  thing   
else4 ,some very ingenious attempts have
 been made to diminish its  size and    
weight1 as in the double gasometer1#ei  
and others1 but without  remarkable     
success4 ,here1 however1 where the room 
required to contain  the gas is directly
 diminished1 the object is so far       
obtained2 and when  that takes place to 
one half1 or even one third1 it is of   
very great  importance4 ,it in a great  
number of cases brings the size of the  
apparatus within what can be allowed in 
private houses2 and in  consequence of  
the rapidity with which the retort can  
be worked1 the  gasometer may again be  
reduced to a still smaller size40       
#ei ,this contrivance is more expensive 
and complicated than any of    the gas  
holders of which a description has been 
given2 nor is it safe1    for if the    
slightest leak should happen in the     
interior vessel of the    double gas    
holder1 an explosive mixture would be   
formed1 and dreadful    consequences    

might follow2 this can never be the case
 with any of the    machines now in     
use4--,note of the ,author4    8,another
 advantage gained by the small quantity 
of gas required for a  flame1 is the    
proportionate diminution of heat arising
 from the lights4  ,the quantities of   
heat and light produced by the          
combustion of  inflammable gases are by 
no means in the same constant relation  
to each  other2 one frequently          
increases1 whilst the other diminishes2 
and this  is eminently the case when    
coal gas and oil gas are burned against 
each  other4 ,the quantity of heat      
liberated is1 speaking generally1 as the
  quantity of gas consumed1 and this is 
greatest with the coal gas2 but  the    
quantity of light is nearly as the      
quantity of carbon that is well  burnt  
in the flame1 and this is greatest in   
the oil gas40    8,the very compact     
state in which the apparatus necessary  
for the  decomposition of oil can be    
placed1 the slight degree of attention  

required1 its certainty of action1 its  
cleanliness1 and the numerous           
applications which it admits of in the  
use of its furnace for other  convenient
 or economical purposes1 render it not  
only unobjectionable1  but useful in    
manufactories and establishments2 and   
these favourable  circumstances are     
accompanied1 not from any inferiority in
 the flame or  increased expense1 but by
 an improved state of the first1 and    
saving in  the latter40    8,messrs4    
,taylor have shewn great ingenuity in   
the construction of their  whole        
apparatus1 but the washer and gasometer 
deserve particular notice  for their    
remarkable simplicity also4 ,in the     
washer1 two planes are  fixed in a box  
or cistern1 in a direction not quite    
horizontal1 but  inclined a little in   
opposite directions2 the planes are     
traversed  nearly across by slips of    
wood or metal1 fixed in an inclined     
position  on the under surface1 and     
which alternately touch one side of the 

cistern1 leaving the other open and     
free4 ,these planes being immersed in   
water1 the gas is thrown in under the   
lowest ridge1 and by its ascending      
power is made to traverse backward and  
forward along the ridges fixed  on the  
planes1 until it escapes at the highest 
part of the uppermost  ridge4 ,thus1    
with a pressure of five or six inches of
 water only1 it is  made to pass through
 a distance of fourteen or sixteen feet 
under the  surface of the fluid1 and    
becomes well washed40    8,the smaller  
gasometers are made of thin plate iron1 
and being placed in  a frame of light   
iron work1 look more like ornamental    
stoves than the  bulky appendages to a  
gas apparatus1 which they supply4 ,the  
larger ones  are made very light1 and   
when in pieces very portable1 by being  
constructed of a frame of wood work1 in 
the edges of which are deep  narrow     
grooves2 plates of iron fit into these  
grooves1 which being  caulked in and    
painted over1 make a light and tight    

apparatus4 ,these are  easily put       
together in any place1 and may therefore
 be introduced into a  small apartment1 
or other confined space1 where a        
gasometer already made  up would not    
enter40    ,for the following additional
 information on this subject1 ,i am     
indebted  to ,messrs4 ,j4 and ,p4       
,taylor4    8,the economy of obtaining  
gas for the production of light from    
oil1 may  be judged of from the         
following data40    8,one gallon of     
common whale oil1 produces about ninety 
cubic feet of  gas4#fj ,an argand burner
 required a cubic foot and a half of gas
 per  hour2 and consequently a gallon of
 oil when converted into gas1 will      
supply the same burner for sixty hours4 
,the expence of the gas at a  moderate  
price of oil1 will be1 allowing for     
coals1 labour1 c4 for  producing the    
gas1 three farthings per hour1 and such 
a burner will give  a light1 equal in   
intensity1 to two argand lamps1 or ten  
mould candles40      #fj ,our           

experiments produced #aje cubic feet1   
from one gallon of    common whale      
oil4--,note of the ,author4    8,the    
expence of an argand oil lamp1 is       
usually admitted to be1 about  three    
halfpence per hour4 ,now supposing ten  
candles to be burning1 four  to the     
pound 7two pound and a half17 they will 
cost #bs4 #aa;d4 of  which one-tenth    
part will be consumed in each hour4 ,the
 cost of the  tallow light is then three
 pence halfpenny per hour40    8,if wax 
candles be employed1 the expence of the 
light equal to an oil  gas burner for   
one hour1 by the same mode of reckoning1
 allowing the  candle to burn ten hours1
 and taking the price of the wax        
candles1 at  #ds4 #f;d4 per pound1 will 
be about #ad;d40    8,the comparative   
account will therefore stand thus3      
,,pence4    ,cost of an ,argand burner1 
supplied with oil gas1 per hour    #j   
,ditto of an ,argand lamp1 burning      
spermaceti oil                 #c       
,ditto of ,tallow mould candles         

#c    ,wax candles                      
#ad    8,these calculations on the cost 
of light from oil gas1 are taken at the 
usual price of good whale oil1 but      
cheaper oils will answer the purpose    
nearly as well1 and as many of these are
 often to be procured1 the whole        
expence becomes materially reduced by   
their use40          ,,part ,,xvi4      
,other products obtainable from ,coal1  
namely3--,coal ,tar--,pitch--,coal      
,oil--,ammoniacal ,liquor1 and          
conversion of the latter into           
,carbonate1 and  ,muriate of ,ammonia4  
,coal ,tar4    ,the coal tar is so      
called from its resembling common tar in
 its  appearance1 and most of its       
qualities4    ,this substance is        
deposited in the purification of the    
coal gas1 in a  separate vessel destined
 to receive it4 ,see fig4 #c1 plate ,i4 
,in the year #affe1 ,becher1 a ,german  
chemist1 brought to ,england his        
discovery for extracting tar from coal1 
this distillation he performed  in close

 vessels4 ,it is not mentioned in the   
records of the time1  whether ,becher   
obtained1 or rather collected1 any other
 articles than  the tar4    ,several    
works have been1 at different times1    
erected both in ,england and  on the    
continent1 to procure from coal a       
substitute for tar2 but they  have      
turned out unprofitable speculations4   
,in #agha1 the ,earl of ,dundonald      
invented a mode of distilling coal in   
the  large way1 which enabled him not   
only to form the coke1 but1 at the same 
time1 to save and collect the tar4 ,even
 this process1 however1 for which  a    
patent was taken out1 gained very little
 ground4 ,its object was too  limited2  
for though some of the proximate        
constituent parts of coal were          
procured1 they were obtained at an      
expence that nearly balanced the        
profits2 and no attention whatever was  
paid to the coal gas1 which  constitutes
 by far the most valuable part          
obtainable from pit coal4    ,coal tar  

is now used with advantage largely in   
the ,royal ,navy1 and also  for painting
 and securing wood that is exposed to   
the action of air4 ,the  wood being     
warmed1 the tar is applied cold1 and    
penetrating into the  pores1 gives the  
timber an uncommon degree of hardness   
and durability4    ,the quantity of tar 
obtainable from a given quantity of     
coal1 varies  according to the manner in
 which the decomposition of the coal is 
affected4 ,see page #abb4    ,the tar   
obtained from ,newcastle coal is        
specifically heavier than that  produced
 from cannel coal2 hence it sinks in    
water1 whereas the latter  swims on the 
surface of that fluid4    ,to render    
coal tar fit for use1 it requires to be 
evaporated to give it  a sufficient     
consistence4 ,if this process be        
performed in close vessels1  a portion  
of an essential oil is obtained1 which  
is known by the name of      ,coal ,oil4
    ,to obtain this oil1 a common still 
is charged with coal tar1 and1 being    

properly luted1 the fire is kindled and 
kept up very moderate1 for the  tar is  
very apt to boil up in the early part of
 the process4 ,the first  product that  
distils over is principally a brown     
ammoniacal fluid1  mixed with a good    
deal of oil4 ,as the process advances1  
and the heat is  increased1 the quantity
 of ammoniacal liquor lessens1 and that 
of oil  increases1 and towards the end  
of the distillation the product is      
chiefly oil4    ,the oil and ammoniacal 
water which distil over do not mix1 so  
that they  may be easily separated by   
decantation4 ,the oil is a yellowish    
inferior  kind of naptha1 which is very 
useful in painting ships1 and for making
  common varnishes4 ,it has lately been 
employed as a substitute for whale  oil1
 to be burnt in out door lamps4    ,the 
contrivance by means of which this oil  
is burnt in lamps#fa  consists of a     
fountain reservoir to supply and        
preserve a constant  level4 ,the burner 
with its wick is placed in the axis of  

the lamp1 and  supplied with the oil    
from the fountain reservoir1 placed on  
the outside  of the lamp4 ,the air is   
admitted by an aperture at the bottom of
 the  lamp4 ,the current of air in      
passing through the lamp envelopes the  
burner and urges the flame1 which is    
extremely bright2 but it is  essential  
that the flame should be small4 ,the    
draught tube proceeding  from the centre
 of the reflector above the flame       
carries away the smoke4      #fa ,all   
the lamps on ,waterloo ,bridge1 and the 
streets adjoining the    bridge are     
lighted by means of tar oil4    #adcj   
pounds of coal tar1 produce #cfj pounds 
of essential oil4 ,the  residue left    
after the distillation is      ,pitch4  
,if the coal tar is wanted to be        
converted into pitch1 without obtaining 
the oil which it is capable of          
furnishing1 the evaporation of it may be
  performed in a common boiler2 but as  
it is extremely liable to boil  over1   
the greatest precaution is necessary in 

conducting the  evaporation4 ,a spout or
 rim is added to the common boiler into 
which the  tar spreads itself as it     
rises1 and by this means becomes cooled1
 and  the boiling over is checked4      
#adcj pounds of coal tar produce #i cwt4
 of pitch4 ,a subsequent  evaporation   
with a gentle heat1 converts the coal   
pitch into a substance  greatly         
resembling asphaltum4      ,manufacture 
of ,carbonate of ,ammonia from the      
,ammoniacal ,liquor of ,pit  ,coal4     
,the ammoniacal liquor obtained in the  
gas light manufacture1 is employed  for 
the production of carbonate of ammonia4 
,the average quantity of this  liquor1  
obtainable from a chaldron1 7#bg cwt47  
of ,newcastle1 or  ,sunderland coal1    
amounts to from #ahj to #bbj pounds4 ,it
 is chiefly  composed of carbonate and  
sulphate of ammonia4 ,the quantity of   
ammonia  contained in it1 varies        
considerably4 ,the strongest liquor is  
obtained  from coal that readily cake1  
7page #de72 a gallon 7or eight and a    

half  pounds weight7 of ammoniacal      
liquor usually requires for saturation1 
from fifteen to sixteen ounces of       
sulphuric acid of a specific gravity    
#a1hd4 ,the weakest ammoniacal liquor is
 obtained from those species of  coal   
which do not cake1 and which by a single
 combustion are reduced to  light ashes4
 ,it requires only from eight to ten    
ounces of sulphuric  acid1 of the before
 mentioned specific gravity for its     
saturation4    ,the following process is
 employed in the large way1 for         
obtaining  carbonate of ammonia from the
 ammoniacal liquor4 ,to #ajh gallons#fb 
of  the liquor contained in a cask1 are 
added #abe pounds#fc of finely  ground  
sulphate of lime1 which has been        
previously deprived of moisture  by     
heat4 ,the cask is bunged up1 and the   
mixture after being stirred  together   
for a few minutes1 is left undisturbed  
for three or four hours4  ,sixteen      
ounces of sulphuric acid are then added1
 the mixture is again  agitated1 and is 

again suffered to stand undisturbed for 
four or six  hours4 ,if the liquor be   
now examined1 it will turn blue litmus  
paper1  red4      #fb ,one gallon of the
 strongest ammoniacal liquor1 weighs    
eight and a    half pounds4      #fc    
,this quantity is evidently too large1  
but the workmen assert1    that an      
excess of sulphate of lime causes the   
carbonate of lime which    is formed1 to
 subside more readily1 and the excess of
 sulphate of lime    can do no injury4  
,in this operation a double             
decomposition takes place1 the sulphate 
of  lime yields part of its sulphuric   
acid1 to the carbonate of ammonia of    
the liquor1 to form sulphate of ammonia1
 and the carbonic acid of the  ammonia1 
combines with the lime of the sulphate  
of lime1 to form  carbonate of lime1    
which falls to the bottom1 the          
supernatant fluid  contains in solution1
 sulphate of ammonia4    ,when the      
liquor has become clear1 it is pumped   
out of the barrel into  shallow cast    

iron boilers1 where it is evaporated    
slowly4 ,during this  process1 a portion
 of sulphate of lime is deposited which 
is removed1  and as the liquor becomes  
more concentrated1 part of the sulphate 
of  ammonia begins to crystallize and   
falls to the bottom4 ,it is shovelled   
out from time to time into wicker       
baskets1 placed slanting over the rim   
of the boiler1 that the liquor which    
drains off from the crystals may  not be
 lost1 and lastly the whole fluid is    
evaporated to dryness4    #ajh gallons  
of ammoniacal liquor from ,newcastle    
coal1 produce upon an  average1 one and 
a half cwt4 of dry sulphate of ammonia4 
,to decompose  it1 one cwt4 is mixt with
 one quarter of a cwt4 of finely ground 
chalk1  previously deprived of moisture 
by heat4 ,the mixture is introduced 7as 
expeditiously as possible7 into cast    
iron retorts1#fd heated nearly to  a    
dull redness1 and when the lid of the   
retorts have been rendered air  tight1  
the fire is raised gradually till the   

retorts are of a strong red  heat4 ,the 
carbonate of ammonia developed from the 
contents of the  retorts1 is made to    
sublime into a leaden barrel-shaped     
receiver1  connected with the retorts1  
by means of a pipe four inches in       
diameter1  proceeding from the upper    
extremity of each retort1 and opposite  
to the  mouth piece4 ,the leaden        
receiver is furnished with a leaden     
cover1  fitting into a groove1 where it 
is made air tight by lute4 ,the receiver
  which is supported upon a stand is    
provided at its base1 with a small      
pipe1 furnished with a stopper4 ,this   
pipe is left open till the liquid       
products are got rid of during the      
sublimatory process4 ,in the centre of  
the cover1 or at any other convenient   
part of the apparatus1 is made a  small 
hole1 slightly stopped with a wooden    
peg1 to give vent to the  elastic fluid 
that becomes evolved during the process4
      #fd ,of the usual form and        
dimensions1 described page #eh4    ,the 

time requisite for the operation depends
 on the mode in which the  retorts are  
set1 the temperature kept up and other  
practical  circumstances4 ,a charge of  
#abj pounds of the mixture of sulphate  
of  ammonia and chalk in one retort1 is 
usually decomposed in twenty-four       
hours4 ,when the operation is at an end1
 and the receiver having become  cold1  
the cover is taken off1 and the sublimed
 carbonate of ammonia  adhering to the  
sides of the receiver is detached by a  
chissel and  mallet1 and after being    
freed from any casual impurities1 is    
packed up  in stone jars for sale4      
,one cwt4 of dry sulphate of ammonia1   
produces from sixty pounds1 to          
sixty-five pounds1 of pure carbonate of 
ammonia4 ,in some establishments1  the  
carbonate of ammonia is subjected to a  
second sublimation by means  of a gentle
 heat2 but this is quite unnecessary if 
the process has been  conducted         
carefully4      ,manufacture of ,muriate
 of ,ammonia from the ,ammoniacal       

,liquor of ,coal4    ,it must be obvious
 that the ammoniacal liquor may be      
employed with great  advantage for the  
production of muriate of ammonia4 ,for  
if the solution  of sulphate of ammonia 
obtained from the ammoniacal liquor by  
means of  sulphate of lime1 as before   
stated1 be mixed with common salt1 7or  
any  other muriate7 another             
decomposition takes place4 ,the muriatic
 acid of  the common salt1 unites to the
 ammonia of the sulphate of ammonia1 and
  produces muriate of ammonia1 and the  
sulphuric acid of the sulphate of       
ammonia1 combines with the soda of the  
common salt1 and produces  sulphate of  
soda1 or glauber salt4    ,the liquor   
containing these two salts being        
evaporated1 the glauber salt  begins to 
crystallize1 and is removed from time to
 time4 ,the evaporation  is continued   
till as much as possible of the glauber 
salt has been  separated1 and the       
muriate of ammonia begins to crystallize
 on the  surface of the fluid in the    

form of a feathered star4 ,the remaining
  fluid is then run off into coolers1   
and deposits little else than  muriate  
of ammonia1 till it gets below the      
temperature of #gf ,fahr4 at  which time
 the crystals are to be removed1 lest   
they should be mixed  with glauber's    
salt which now begins to be again       
deposited4 ,after the  muriate of       
ammonia has been suffered to drain in   
baskets1 it is heated  in shallow pans  
to drive off as much water of           
crystallization as  possible4 ,it is    
then removed whilst still hot1 into     
earthenware jars1  glazed within1 and   
fitted with a cover1 7having a hole of  
about half an  inch in diameter in its  
centre17 luted on with clay4 ,the jars  
are put in  a cast iron pot over a      
strong fire1 in a furnace capable of    
containing  from six to eighteen jars1  
surrounded with sand up to the edge of  
the  pot1 and also having about two and 
a half inches of sand on the cover1     
confined by an iron ring about three    

inches deep1 and two inches less in     
diameter than the cover1 in order that  
if the luting should give way in  any   
part1 it may be repaired without        
suffering the covers 7which should  be  
kept during the sublimation at about    
#cbj ,fahr47 to be cooled by the        
removal of a large portion of the sand4 
,these earthen jars may be filled to    
within two inches of the top1 with  the 
dried salt gently pressed in1 but not   
rammed close2 and the fire  which has   
been lighted some time before1 is now to
 be raised gradually  till the iron pots
 are of a pretty strong red heat all    
round1 being so  placed by mean of flues
 in the furnace that the upper part may 
be first  heated1 the bottom resting on 
solid brick work4    ,during the first  
impression of the heat1 a portion of the
 salt carrying  with it a quantity of   
watery vapour not separated during the  
drying of  the salt1 will escape through
 the hole in the cover1 which must be   
left  open till all the aqueous part is 

exhaled3 this is known by bringing a    
piece of cold smooth iron plate near the
 hole1 in order to condense the         
sublimate1 which becoming more and more 
dry1 at length attaches itself  firmly  
to the plate1 in the form of a dry      
semi-transparent crust4    ,at this time
 the hole is to be stopped with lute1   
more sand is to be put  on the cover1   
and the heat continued till it is judged
 that nearly the  whole of the muriate  
of ammonia is sublimed4 ,the time       
requisite for this  purpose depends on  
the construction of the furnace1 the    
size of the  pots1 the briskness of the 
fire1 and other circumstances only to be
  learnt by experience4    ,the process 
should be stopped before the sublimation
 has entirely  ceased1 as the heat in   
some parts of the jar may be too great  
when it is  nearly empty1 and either by 
volatilizing a part of the salt itself1 
or  elevating a portion of foreign      
matter from which it can never be kept  
wholly free1 and thus giving the cake a 

yellow tinge1 and a scorched1  opake1   
crackled appearance4    ,the same       
defects are likely to happen1 when any  
part of the luting  having given way1 is
 obliged to be repaired by wet lute1    
when the  sublimation is pretty far     
advanced3 consequently glass vessels are
  preferable1 except on account of the  
expence1 as they must always be  broken 
to pieces in order to get out the cake3 
the earthenware jars on  the contrary   
will serve for several sublimations1    
even the covers1 if  well glazed1 will  
last two operations4 ,the sublimation   
being finished  and the apparatus having
 become sufficiently cool1 the tops of  
the jars  are to be taken off1 and the  
cakes of sal-ammoniac that are found    
adhering to them are to be separated1   
and placed for a day or two in a  damp  
atmosphere1 which softens their surface 
a little1 and thus  facilitates the     
removal of any superficial impurities4  
,lastly1 the cakes  are packed up in    
casks for sale4    ,the excise laws have

 hitherto operated strongly against the 
establishment of manufactories of       
muriate of ammonia in ,england4 ,hence  
an immense quantity of sulphate of      
ammonia obtained from the gas light     
ammoniacal liquor1 is exported from this
 country to the continent1  solely from 
the extreme rigour of the excise        
relating to the use of  common salt1 and
 it is only this that has hitherto      
prevented the  establishment of         
manufactories of sal-ammoniac from the  
ammoniacal  liquor of the gas light     
process upon a large scale4    ,chemical
 manufactories1 of all others1 will     
least bear excise1 because  many of them
 are worked according to secret         
processes1 which1 if made  public1 must 
pass into other countries2 and the      
greatest part of the  profit ceases     
together with the export4 ,the vexatious
 introduction of  excise officers into  
manufacturing laboratories1 it is       
evident1 puts an  end to all secrecy of 
operation4 ,there are several chemical  

processes  which interruption will      
extremely injure1 and others which it   
totally  destroys1 and as on the whole  
they in general are of a nature in which
  interference of others is most        
peculiarly vexatious1 in all            
probability1  if the excise be extended 
to manufactures of this nature1 it will 
eventually put a stop to most of them1  
and greatly injure the revenue by       
causing thereby to cease the duties     
which at present arise from the  exports
 and imports to a large amount1 now     
depending on the chemical  trade of     
,great ,britain4    ,we have now gone   
through all the improvements by which   
the gas light  manufacture has been     
distinguished during the interval which 
has elapsed  since the publication of   
our former work#fe on this subject2 and 
perhaps the reader may be inclined to   
think1 from the extraordinary  height to
 which improvement has been carried in  
this art1 that little or  nothing more  
remains to be desired with regard to it4

 ,let it be  remembered1 however1 that  
the whole art is only in its infancy4   
,there is  yet a wide field for         
improvement in the construction of the  
apparatus4  ,ingenious men may speculate
 from what has been done1 to what       
remains to  be effected1 which no doubt 
will lead to objects of the greatest    
utility1 and most extended national     
importance4      #fe ,a practical       
treatise on gas light4                  
,,description ,,of ,,the ,,plates4      
,,plate ,i4                             
,,page4      ,elevation of the          
,revolving ,gas ,holder at the          
,westminster ,gas    ,works             
#aha        ,,plate ,,ii4      ,gas     
,light ,apparatus at the ,royal ,mint4  
,fig4 #a1 ,perpendicular ,section of one
 of the ,horizontal ,rotary    ,retorts 
with its ,furnace                       
#aab      ,fig4 #b1 ,the ,purifying     
,apparatus                              
#aej      ,fig4 #c1 ,the ,tar ,cistern  
#aag      ,fig4 #d1 ,the ,gas ,metre    

#bad      ,the roof of the building     
surrounding the ,gas ,works is furnished
    with a projecting ,louver to let out
 the smoke4        ,,plate ,,iii4       
,fig4 #a1 ,represents a perspective view
 of a ,portable ,gas ,metre      #bai   
,fig4 #b1 ,perpendicular ,section of the
 ,horizontal ,rotary ,retorts at    the 
,royal ,mint ,gas ,works--at            
,chester--,birmingham1 c4               
#aab      ,fig4 #c1 ,perpendicular      
,section of the ,gas ,holder ,valve and 
,siphon1    or ,water ,reservoir        
#bbb      ,fig4 #d1 ,perspective ,view  
of the ,governor1 or ,regulating ,guage1
    for maintaining the ,flames of ,gas 
,lamps and ,burners of an uniform       
intensity                               
#bbe      ,fig4 #e1 ,plan of the        
,horizontal ,rotary ,retorts at the     
,royal                                  
,mint--,chester--,bristol--,birmingham--
,kidderminster1 c4             #aae     
,fig4 #f1 ,transverse ,section of the   
,gas ,metre at the ,royal               

,mint--,chester--,birmingham1 c4        
#bai      ,fig4 #g1 ,perpendicular      
,section of the ,gas ,holder ,valve     
#bba      ,fig4 #h1 ,front elevation of 
the ,gas ,metre1 at the ,royal ,mint1   
shewing the registering train of ,wheel 
,work                        #bah       
,fig4 #i1 ,perpendicular ,section of the
 ,gas ,holder1 ,governor1 or            
,regulating ,guage1 at the              
,bristol--,birmingham--and ,chester ,gas
    ,works                              
#aga      ,fig4 #aj1 ,transverse        
,section of the ,air-,box1 and ,lime    
,trough1 ,see    purifying apparatus    
#aeb      ,fig4 #aa1 ,perspective ,view 
of a ,portable ,governor or ,regulating 
,guage                                  
#bcb      ,fig4 #ab1 ,coal ,tray of     
,horizontal ,rotary ,retort             
#aaf      ,fig4 #ac1 ,a jointed swing   
,bracket ,lamp                          
#beg      ,fig4 #ad1 ,a ,mercurial      
,universal ,joint for ,pendent ,gas     
,lamps         #bef        ,,plate ,,iv4

      ,fig4 #a1 ,transverse ,section of 
the ,retort ,ovens1 at the ,westminster 
and ,city of ,london ,gas ,works1       
showing the mode of setting and         
arranging ,cylindrical ,retorts         
#fi      ,fig4 #b1 ,longitudinal        
,section of the same                    
#fi        ,,plate ,v4      ,fig4 #a1   
,front elevation of the ,retort ,ovens  
at the ,westminster and    ,city of     
,london ,gas ,works                     
#fi      ,fig4 #b1 ,perpendicular       
,section of the ,gas ,holder1 without   
,specific    ,gravity ,apparatus1 at the
 ,birmingham ,gas ,works                
#agg      ,fig4 #c1 ,plan of the same   
#agg      ,fig4 #d1 ,perpendicular      
,section of ,mr4 ,malam's ,lime ,machine
          #adc      ,fig4 #e1 ,plan of  
the same                                
#adf      ,fig4 #f and #g1 ,mouth ,piece
 and ,cover of cylindrical1             
parallelopipedal and semi-cylindrical   
,retorts1 7exhibited fig4 #a1    plate  
,,iv17 drawn to a larger scale          

#ga      ,fig4 #h1 #i1 #aj1 #aa1 #ab1   
and #ac1 ,gas ,lamps and ,burners       
#bec      ,fig4 #ad and #ae1 ,profile   
,view and ,section of ,gas ,mains1 and  
mode of    connecting them              
#bdj      ,fig4 #af1 #ag1 and #ah1      
,perpendicular ,section of the          
parallelopipedal1 ellipsoidal1 and      
semi-cylindrical ,retorts         #ec   
,fig4 #ai1 #bj1 #ba1 and #bb1 ,union    
,joint1 and circular bends for          
connecting ,gas ,pipes                  
#bff      ,fig4 #bc1 ,test ,apparatus   
for certifying the proper manner of     
working the ,lime ,machine              
#aeg        ,,plate ,,vi4      ,fig4 #a1
 ,plan1 showing the ,fire ,place and    
,flues1 of the ,horizontal    ,rotary   
,retorts                                
#aac      ,fig4 #b1 ,longitudinal       
,section of the ,collapsing ,gas        
,holder1 and    the ,tank of ditto      
#ahi      ,fig4 #c1 ,transverse ,section
 of the same                            
#ahi      ,fig4 #d1 ,end ,view of the   

same                                    
#ahi      ,fig4 #e and #f1 ,horizontal  
plan shewing the mode of connecting the 
end plates of the ,collapsing ,gas      
,holder                            #aib 
,fig4 #g1 ,perpendicular ,section of the
 ,gas ,holder1 without specific         
gravity ,apparatus1 at the ,chester ,gas
 ,works                        #age     
,fig4 #h1 ,perspective ,view of the     
,revolving ,gas ,holder1 at the         
,westminster ,gas ,works                
#aha      ,fig4 #i1 ,perspective ,view  
of the ,reciprocating ,safety ,valve    
#aif      ,fig4 #aj1 ,plan of the       
,purifying ,apparatus1 or ,lime         
,machine1 shewing    the ,air ,trough of
 the ,apparatus1 with its axis and claws
           #aeb      ,fig4 #aa1 ,sliding
 part of a ,pendent ,gas ,lamp1 which   
may be raised    or depressed           
#beg        ,,plate ,,vii4              
,exhibits an economical arrangement of a
 ,gas ,apparatus1 for lighting a        
town1 or large districts4 ,the central  

building exhibits the ,retort    ,house4
 ,the roof is furnished with a          
projecting ,louver to let out the       
smoke4 ,the gable ends1 and one side of 
the building1 are of    brick-work1 the 
other side of the house is open1 and    
supported on iron    columns4 ,the      
building to the right hand side of the  
,retorts1 is the    ,purifying ,house1  
it contains the ,lime ,machine1 page    
#adi4 ,the trap    door1 marked ,a1     
indicates the ,cistern or ,reservoir for
 receiving the    ,waste ,lime4 ,the    
third and smallest building in the      
design1 serves for    an ,office of the 
,director of the ,works4 ,the front wall
 is represented    as taken away1 to    
show the position of the ,gas ,metre1   
the axis of    which drives the         
agitating shaft of the ,lime ,machine4  
,the axis of the    ,metre and the shaft
 of the ,lime ,machine1 are for that    
purpose    connected by a strap1 7page  
#bac47 ,the small building-on the left  
hand    side of the ,retort ,house1 is a

 ,smith's ,shop4 ,t1 shows the situation
 of    the ,main ,gas ,holder ,valve    
7page #bba47          ,,index4          
,a4      ,advantages of the art of      
procuring light by means of coal gas    
#a      ,air box of lime machine        
#aec      ,ammoniacal liquor1 quantity  
obtainable from a given quantity of     
coal                                    
#cjc      ,ammoniacal liquor1 quantity  
of sulphuric acid1 required for         
saturating a given quantity             
#cjc      ,ammoniacal liquor1 conversion
 of1 into carbonate of ammonia          
#cjc      ,ammoniacal liquor1 conversion
 of1 into muriate of ammonia            
#cjc      ,apparatus for obtaining      
carburetted hydrogen gas from coal tar  
#bhe      ,apparatus for purifying coal 
gas                                     
#ada      ,apparatus for certifying the 
proper mode of working the lime         
machine                                 
#aeg      ,argand gas lamp              
#bec      ,argand gas lamp1 quantity of 

gas consumed by different kinds         
#bge      ,art of procuring coal gas1   
theory of                               
#cc        ,b4      ,bat's wing gas     
burner                                  
#bee      ,bends1 for connecting gas    
pipes                                   
#bfg      ,burner1 argand               
#bec      ,burner1 bat's wing           
#bee      ,burner1 cockspur             
#bee      ,branch pipes                 
#bci      ,branch pipes1 dip of         
#bdc      ,branch pipes1 mode of        
connecting                              
#bfc      ,branch pipes1 mode of proving
                                        
#bfe      ,branch pipes1 corrosion of   
#bfj        ,c4      ,carbonate of      
ammonia1 preparation of1 from ammoniacal
 liquor of    coal                      
#cjc      ,cement1 for connecting gas   
mains                                   
#bda      ,chandelier1 sliding1 for     
burning gas                             
#beg      ,chester gas holder1          

description of                          
#age      ,coal1 analysis of1 by        
destructive distillation                
#ce      ,coal1 chemical constitution of
                                        
#db      ,coal1 classification of       
#da      ,coal1 comparative facility    
with which different species are        
decomposed                              
#ajf      ,coal1 chiefly composed of    
bitumen only1 varieties of              
#db      ,coal1 chiefly composed of     
bitumen1 maximum quantity of gas        
obtainable from them                    
#dc      ,coal1 containing more carbon  
than bitumen                            
#de      ,coal1 containing more carbon  
than bitumen1 maximum quantity of gas   
obtainable from them                    
#dh      ,coal1 destitute of bitumen    
#db      ,coal1 maximum quantity of gas 
obtainable from them                    
#dd      ,coal1 ,gloucestershire        
#di      ,coal1 ,kilkenny               
#dd      ,coal1 ,lancashire             

#dd      ,coal1 ,newcastle              
#dg      ,coal1 ,scotch                 
#aji      ,coal1 ,warwickshire          
#aji      ,coal1 ,welch ,stone          
#dh      ,coal1 ,yorkshire              
#dd      ,coal oil                      
#cjj      ,coal oil1 quantity obtainable
 from a given quantity of coal tar      
#cjb      ,coal tar                     
#bih      ,coal tar1 quantity obtainable
 from a given quantity of coal          
#abb      ,coke1 quantity obtained in   
the gas light process from a given      
quantity of coal1 by means of           
cylindrical retorts                     
#acb      ,coke1 quantity obtained by   
means of horizontal rotary retorts      
#acb        ,f4      ,flue plan of      
setting cast iron retorts               
#ei      ,flue plan1 report on a series 
of operations1 made with retorts        
worked on the flue plan                 
#fa      ,fuel1 minimum quantity        
required for the complete decomposition 
of    coal1 by means of cylindrical     

retorts                                 
#fa        ,g4      ,gas1 average cost  
of manufacturing it upon a large scale1 
in    ,london                           
#ajf      ,gas1 apparatus for lighting a
 town1 best situation of1 as far as     
it regards the most economical          
distribution of the pipes           #bdi
      ,gas1 apparatus for lighting a    
town1 arrangement of                    
#cai      ,gas1 apparatus for lighting a
 town1 at the ,royal ,mint              
#aab      ,gas1 burners1 different kinds
 of                                     
#bec      ,gas1 quantity of1 evolved    
during different periods of the         
distillatory process employed for       
decomposing coal1 in    cylindrical     
retorts                                 
#gg      ,gas1 observations on the      
progressive evolution of1 during        
different periods of the distillatory   
process with cylindrical    retorts     
#gi      ,gas flame1 mode of regulating 
the magnitude of                        

#bcd      ,gas holder1 construction of1 
originally employed                     
#afd      ,gas holder1 sheet iron1 best 
adapted for it                          
#ahj      ,gas holder1 sheet iron1 best 
adapted for it1 cost of                 
#afd      ,gas holder1 sheet iron1      
lately adopted without specific gravity 
apparatus                               
#afi      ,gas holder1 at ,birmingham   
without specific gravity apparatus      
#agg      ,gas holder1 at ,bristol      
without specific gravity apparatus      
#age      ,gas holder1 at ,chester      
without specific gravity apparatus      
#age      ,gas holder1 collapsing       
#ahe      ,gas holder1 collapsing1 rule 
for finding its capacity                
#aie      ,gas holder1 revolving at the 
,westminster gas works                  
#aha      ,gas holder1 collapsing1 rule 
for calculating its capacity            
#ahe      ,gas holder1 valve            
#bba      ,gas from coal tar            
#bhf      ,gas from coal tar1 average   

quantity obtainable from a given        
quantity of tar                         
#bhf      ,gas from oil                 
#bhi      ,gas from oil1 quantity       
obtainable from a given quantity of oil 
#big      ,gas from vegetable tar       
#bhd      ,gas from vegetable tar1      
average quantity obtainable from a given
    quantity of tar                     
#bhd      ,gas illuminating power of    
#bga      ,gas lamps                    
#bec      ,gas lamps1 diameter of the   
pipes for supplying them with gas       
#bfa      ,gas mains                    
#bci      ,gas mains1 mode of proving   
them when laid                          
#bde      ,gas mains1 observations on   
#bdg      ,gas mains1 cost of a mile1   
laid under ground in ,london            
#beb      ,gas mains1 of pewter1 lead1  
and tin1 why unfit for distributing     
gas                                     
#bfj      ,gas mains1 weight of         
different lengths1 of a given bore      
#bea      ,gas metre1 construction of   

#bad      ,gas metre1 construction of1  
at the ,royal ,mint ,gas ,works         
#bad      ,gas metre1 directions to     
workmen for fixing it                   
#bbi      ,gas metre1 rule for          
calculating its power                   
#bbj      ,gas metre1 at the ,birmingham
 ,gas ,works1 registering capacity of   
#bbj      ,gas metre1 at the ,bristol   
,gas ,works1 registering capacity of    
#bbj      ,gas metre1 at the ,chester   
,gas ,works1 registering capacity of    
#bbj      ,gas pipes1 directions to     
workmen for adapting them to the        
interior of houses                      
#beh      ,gasometer house1 of sheet    
iron1 of a given size1 cost of          
#agh      ,gasometer1 tank of cast iron1
 of a given size1 cost of               
#agh      ,gasometer1 tank of brick     
work1 of a given size1 cost of          
#agh      ,gasometer1 tank of wood1 of a
 given size1 cost of                    
#agh      ,governor1 or regulating guage
                                        

#bfa      ,governor1 its application and
 efficacy                               
#aga      ,governor1 directions to      
workmen for fixing it                   
#bbi        ,h4      ,horizontal rotary 
retort4 7,see rotary retort horizontal7 
#aaj        ,l4      ,lamps for burning 
coal gas                                
#bec      ,lamps for burning coal gas1  
quantity of gas consumed by different   
kinds1 in a given time                  
#bge      ,lime machine originally      
employed1 defects1 and dangerous        
consequences to which it gave rise      
#ada      ,lime machine1 lately adopted 
#adi      ,lime machine1 at ,birmingham 
gas works                               
#adi      ,lime machine1 at ,chester gas
 works                                  
#adi      ,lime machine1 at ,royal ,mint
 gas works                              
#aej      ,lime machine1 capacity       
requisite for purifying a given volume  
of    gas in a given time               
#aeg        ,m4      ,mains for         

conveying gas                           
#bde      ,mains1 average cost of a mile
 when laid in ,london                   
#beb      ,mains1 manner of proving them
 when laid                              
#bde      ,mains1 kind of1 most         
economical for conveying gas            
#bea      ,mains1 which do not supply   
branch pipes or lamps1 observations on  
#bej      ,mains1 faulty1 how           
distinguished                           
#bdj      ,mercurial joint for pendent  
gas lamps                               
#bef      ,muriate of ammonia1          
preparation of1 from the ammoniacal     
liquor of    coal                       
#cjc        ,n4      ,newcastle coal1   
maximum quantity of gas obtainable from 
different    kinds                      
#dg        ,o4      ,oven1 for heating  
retorts1 7,see retort oven7      ,oil1  
from coal tar                           
#cjj      ,oil gas                      
#bhi      ,oil gas1 quantity obtainable 
from a given quantity of whale oil      

#bif      ,oven plan1 of setting cast   
iron retorts                            
#fg        ,p4      ,pendent gas lamp   
#beg      ,pipes1 directions to workmen 
for adapting them to the interior of    
houses                                  
#beh      ,pitch from coal tar          
#cjb      ,pitch1 quantity obtainable   
from a given quantity of tar            
#cjb      ,purifying apparatus1 7,see   
lime machine7                           
#aej        ,q4      ,quicklime1 best   
method of preserving it for the         
purification of    coal gas             
#afj      ,quicklime1 quantity required 
for purifying a given volume of coal    
gas                                     
#afb        ,r4      ,reciprocating     
safety valve                            
#aif      ,regulating guage1 regulator1 
or governor                       #aga  
#bbj      ,regulating guage1 at         
,birmingham ,gas ,works                 
#agg      ,regulating guage1 at ,bristol
 ,gas ,works                            

#agg      ,regulating guage1 at ,chester
 ,gas ,works                            
#agg      ,retorts1 cylindrical cast    
iron                                    
#eb      ,retorts1 cylindrical1 method  
of heating them by flues                
#ei      ,retorts1 cylindrical1         
experiments on setting three to one fire
    place                               
#fa      ,retorts1 cylindrical1         
experiments on setting four to one fire 
place                                   
#ec      ,retorts1 cylindrical1 cost of 
erecting them                           
#ii      ,retorts1 cylindrical1 best    
mode of working them                    
#id      ,retorts1 cylindrical1 minimum 
quantity of fuel required for    working
 them                                   
#fa      ,retorts1 cylindrical1         
temperature best adapted for working    
them     #id      ,retorts1 cylindrical1
 conical                                
#eb      ,retorts1 cylindrical1 conical1
 comparative power of                   

#ee      ,retorts1 cylindrical1         
ellipsoidal                             
#ec      ,retorts1 horizontal rotary    
#aaj      ,retorts1 horizontal rotary1  
at the ,royal ,mint ,gas ,works         
#aab      ,retorts1 horizontal rotary1  
at ,birmingham                          
#aaa      ,retorts1 horizontal rotary1  
at ,chester                             
#aaa      ,retorts1 horizontal rotary1  
at ,kidderminster                       
#aaa      ,retorts1 horizontal rotary1  
action and management of                
#aba      ,retorts1 horizontal rotary1  
advantages of                           
#abd      ,retorts1 horizontal rotary1  
directions to workmen with regard to    
working them                            
#acd      ,retorts1 parallelopipedal    
#eb      ,retorts1 parallelopipedal1    
comparative power of                    
#ee      ,retorts1 parallelopipedal1    
best mode of working them               
#ic      ,retorts1 semi-cylindrical     
#ec      ,retorts1 oven1 description of1

 at the ,westminster and ,city of       
,london ,gas ,works                     
#fi      ,retorts1 oven1 experiments on 
#hd      ,revolving gas holder1 at the  
,westminster ,gas ,works                
#aha      ,revolving gas holder1 rule   
for calculating its capacity            
#ahe        ,s4      ,safety valve1     
reciprocating                           
#aif      ,self-acting guage1 7see      
governor7                               
#aga      ,siphon                       
#bba      ,sliding chandelier           
#beg      ,south ,london ,gas ,works    
#fi      ,spigot and faucit pipes       
#bda      ,staffordshire coal           
#dd      ,swing bracket gas burner      
#beg        ,t4      ,tar1 quantity     
obtainable from a given quantity of coal
             #acj      ,tar gas1        
quantity obtainable from a given        
quantity of coal tar     #bhg      ,tar 
gas1 from vegetable tar                 
#bhd      ,tar1 retort                  
#bhe      ,temperature for working cast 

iron retorts1 remarks on                
#id      ,test apparatus1 for certifying
 the proper manner of working the       
lime machine                            
#aeg      ,theory of the production of  
gas lights                              
#ci      ,towns lighted with gas        
#adi        ,v4      ,valve of gas      
holder                                  
#bba      ,valve1 hydraulic             
#aaf      ,valve1 of horizontal rotary  
retort                             #aaf 
#abd      ,valve1 lime machine          
#aef      ,valve1 reciprocating         
#aif      ,ventilation of rooms lighted 
by gas                                  
#bgf        ,w4      ,water reservoir1  
7,see ,siphon7                          
#bba      ,wheel work1 registering of   
gas metre                               
#bah          ,,london ,,price ,,list   
,of the most essential articles employed
 in the manufacture and  application of 
,coal ,gas2 delivered free of expence at
 any ,wharf between  ,london and        

,vauxhall ,bridge4      ,cast iron      
,spigot and ,faucit ,pipes4             
,,diameter4             ,,thickness ,,in
 ,,the ,,metal4    ,,price ,,per ,,yard4
                                        
4    s4 d4    #a and a half inch        
#e-sixths of an inch             #b     
#f    #b inches                         
#c-;eighths                       #c    
#f    #b and a half ditto        ditto  
#d    #j    #c inches                   
#g-sixteenths                    #d     
#f    #d ditto                 half an  
inch                    #f    #f    #e  
ditto                   ditto           
#i    #j    #f ditto                    
ditto                        #aj    #j  
#g ditto                   ditto        
#aa    #j    #h ditto                   
#e-;eighths                      #ab    
#c    #i ditto                   ditto  
#af    #f    #aj ditto                  
ditto                        #ai    #f  
,cast iron ,flanch ,pipes4      #a and a
 half inch                              

#c    #j    #b inches                   
#d    #j    #b and a half inch          
#d   #aj    #c inches                   
#e    #d    #d ditto                    
#g    #c    #e ditto                    
#i    #f    ,quadrant flanch pipes      
#ad    #j cwt4    ,bend pipes of        
different radii1 branch pipes and       
accommodating pipes                     
#ac    #j cwt4    ,from eight to six    
inches #acs4 #f;d4 from #e to #c        
inches                                  
#ad    #j    ,two1 and #a and a half    
inch                             #ad    
#f    ,siphon1 water reservoir1 or      
tar-well pipes1 from #b    to #f inches 
in diameter                             
#ae    #j cwt4    ,ditto1 above #f      
inches in diameter                      
#ad    #j    ,gas holder1 or hydraulic  
valve pipes1 with boxes       #ae    #j 
,wrought iron work and screws to ditto  
#j    #g     ,retorts of best picked    
iron1 from second process       #ac     
#j cwt4    ,mouth pieces to ditto1      

ground and fitted               #bj     
#j    ,wrought iron work and screws to  
ditto                   #j    #g        
,connecting and stride pipes1 ground    
#bj    #j cwt4    ,hydraulic cylinders  
#ae    #j    ,tapering pipes            
#ae    #j    ,outer fire doors          
#ae    #j    ,inner ditto               
#aa    #j    ,fire back1 bearers1 dead  
plates                        #aa    #j 
,top1 register1 and slide dampers       
#ad    #j    ,pullies1 and friction     
sectors1 turned and fitted       #bb    
#j    ,wrought iron gudgeons for ditto1 
turned and fitted      #a    #j 4       
,one inch bolts           ,seven-eighths
 ditto   at                           #j
   #j    #e 4    ,three-quarters ditto  
,five-eighths                           
#b   #h    #j gross4    ,half-inch      
#a  #ah  #j gross4    ,tar receivers and
 purifying vessels                 #j   
#ad  #j cwt4    ,condensing pipes1 and  
inlet and outlet pipes for    tanks     
#j  #ad  #j    ,cast iron tanks put     

together complete1 with bolts1          
screws1 cement1 c4                      
#j  #af  #j    ,gas holders1 original   
construction1 erected    complete of    
sheet iron                              
#j  #fj  #j    ,gas holder1 collapsing  
ditto1 complete1 capacity    #cj1jjj    
cubic feet                              
#ajjj   #j  #j    ,gas holder1          
collapsing ditto1 complete1 capacity    
#ae1jjj cubic feet                      
#gjj   #j  #j    ,gas holder1 collapsing
 ditto1 complete1 capacity    #bb1jjj   
cubic feet                              
#hjj   #j  #j      ,wrought iron ,gas   
,tubes screwed and fitted1 warranted to 
bear a pressure  equal to a column of   
water #cjj feet high4         ,,bore4   
,,pence ,,per ,,foot4    #a inch        
#aj    #g-;eighths                      
#h    #c-quarters                    #g 
#e-;eighths                     #g      
,half an inch and #c-;eighths    #f     
,copper ,tubes4          ,,bore ,,of    
,,tube4                                 

,,price ,,per ,,foot4                   
s4 d4       #c-;eighths of an inch      
copper tubes                   #j    #d 
,half ditto             ditto           
#j    #f       #e-;eighths ditto        
ditto                        #j    #i   
#c-quarters ditto       ditto           
#j   #aa       #g-;eighths ditto        
ditto                        #a    #d   
#a inch                 ditto           
#a    #h       #a and a half ditto      
ditto                        #b    #b   
,union joints #c-;eighths of an inch    
#hs4 half an    inch #is4 #e-;eighths of
 an inch #ajs4 #f;d4    #c-quarters of  
an inch                             #j  
#ad    #j per doz4    ,union ,t sockets1
 #c-quarters of an inch #bjs4    half   
inch                                    
#j   #ad    #j per doz4                 
,three-quarters of an inch main cocks   
#j    #d    #f each      ,brazed sheet  
iron ,tubes4        ,,bore ,,of ,,tube4 
,,price ,,per ,,foot4                   
s4  d4    #c-;eighths of an inch        

#j  #c    ,half an inch                 
#j  #d    #e-;eighths of an inch        
#j  #e    #c-quarters                   
#j  #f    #a inch                       
#j  #g    #a and a quarter              
#j #aj    #a and a half                 
#a  #c                                  
4 s4 d4    ,ornamental gas lamp posts1  
and columns1 fitted    complete with    
,york lamps glazed1 tube1 branches1     
cocks1 and burners1 ready for lighting  
4 #f    #f    #j each    ,or castings   
for ditto                               
#ac    #j cwt4    ,wrought iron work for
 ditto                               #j 
#g 4    ,argand burners complete1 from  
#bs4 #f;d4 to              #e    #j each
    ,iron roofs for retort and gas      
holder houses1    erected complete1 at 4
 #f #f #j per square of #ajj    feet1   
superficial measure4      ,cost of      
laying cast iron ,gas mains in ,london4 
,to take up the ground1 to  fill in1 but
 not to re-pave the ground1 and to drive
 two and a half  inches of lead into the

 joints of the pipes4      ,,diameter   
,,of ,,mains4        ,,per ,,yard4      
s4 d4     #c inches                  #a 
#f     #d ditto                   #a    
#aj     #e ditto                   #b   
#a     #f ditto                   #b    
#b     #g ditto                   #b    
#d     #h ditto                   #b    
#g     #i ditto                   #c    
#j    #aj ditto                   #c    
#d                                      
4 s4 d4    ,tapping the mains and laying
 gun barrel1 or    branch pipes         
#j   #a    #j per yrd4    ,governor     
complete to regulate every #bd hours    
#cj1jjj cubic feet of gas               
#fj   #j    #j    ,a lime machine1 new  
construction1 to purify    #cj1jjj cubic
 feet of gas every #bd hours            
#bbj   #j    #j    ,a gas metre1 to     
register #cj1jjj cubic feet of    gas   
every #bd hours                         
#aje   #j    #j    ,a gas light         
apparatus complete1 capable of          
producing #dh1jjj cubic feet of gas     

every #bd    hours1 costs1 if erected in
 ,london              #hjjj   #j    #j  
,,estimate    ,,of    ,a ,gas ,light    
,apparatus1    ,capable of producing    
every #bd hours1 a light equal to       
#ba1ccj tallow    candles1 eight in the 
pound1 burning for six hours4           
4 s4 d4      ,five horizontal rotary    
retorts1 #ab feet #f inches in          
diameter1 complete for immediate use    
#bcbj   #j    #j    ,two lime machines1 
ditto ditto                             
#ecf   #j    #j    ,two collapsing gas  
holders1 #cj1jjj cubic feet capacity    
each                                    
#bjjj   #j    #j    ,a gas metre        
#bjj   #j    #j    ,a governor or       
regulating guage                        
#ajj   #j    #j    ,tar well            
#eh   #j    #j    ,pumps                
#fg   #j    #j    ,connecting pipes     
#bfe   #j    #j    ,condensing pipes1   
between the retorts1 tar well1 and      
lime machines                           
#bai  #af    #j    ,retort house1 with  

iron roof                               
#fec  #ai    #j    ,lime machine house1 
with ditto ditto                    #bcj
   #j    #j    ,workmen's tools and     
sundries                            #dcj
   #j    #j                             
----------------                        
4 #gjgi  #ae    #j    ,this apparatus is
 capable of producing every #bd hours1  
#ff1jjj cubic feet  of gas4      ,,the  
,,end4        ,c4 ,green1 ,printer1 #ae1
 ,leicester ,street1    ,leicester      
,square4          ,in the ,press1    ,a 
,,description ,,of ,,the ,,chemical     
,,apparatus ,,and ,,instruments1        
,,with ,,fifteen ,,quarto ,,copper      
,,plates1    ,,by ,,fredrick ,,accum4   
,,works    ,,lately ,,published ,,by    
,,fredrick ,,accum4      ,a ,,practical 
,,essay ,,on ,,chemical ,,re-,,agents   
,,or ,,tests1    ,exhibiting the general
 nature of ,chemical ,re-,agents or     
,tests--the  ,effects which they produce
 upon different bodies--the ,uses to    
which they  may be applied1 and the ,art

 of applying them successfully4    ,,the
 ,,second ,,edition1    ,illustrated by 
a ,series of ,experiments4 ,price #is4  
,,chemical ,,amusement1    ,comprising a
 ,series of curious and instructive     
,experiments in ,chemistry1  which are  
easily performed1 and unattended by     
,danger4    ,the ,fourth ,edition4      
,price #is4      ,a ,,practical         
,,treatise ,,on ,,gas ,,light1    ,,with
 ,,seven ,,coloured ,,plates1           
,exhibiting a summary description of the
 ,apparatus and ,machinery best         
calculated for illuminating ,streets1   
,houses1 and ,manufactories1 with  ,coal
 ,gas2 with ,remarks on the general     
nature of this new branch of civil      
economy4    ,the ,fourth ,edition4      
,price #abs4      ,,elements ,,of       
,,crystallography1    ,after the ,method
 of ,hay1    ,,with ,,plates ,,and      
,,graphic ,,designs1    ,exhibiting the 
,forms of ,crystals1 their ,geometrical 
,structure1 and  general ,laws1         
according to which the immense variety  

of actually  existing ,crystals are     
produced4    ,price #aes4      ,a       
,,manual ,,of ,,analytical ,,mineralogy1
    ,intended to facilitate the         
,practical ,analysis of ,minerals1 by   
pointing  out to the ,student concise   
directions for performing the ,analysis 
of  ,metallic ,ores1 ,earths1 and other 
,minerals4    ,second ,edition4 #b      
,vols4 ,price #aes4      ,a ,,system    
,,of ,,theoretical ,,and ,,practical    
,,chemistry1      ,,in ,,two ,,vols4    
,,with ,,plates4    ,second ,edition4   
,price #aes4          ,directions to the
 ,binder4      ,plate ,,ii1 to face     
,title ,page4    ,plate ,,iii1 ,,iv1 ,v1
 ,,vi1 and ,,vii1 at the end of the     
,book4          ,illustration3 ,pl4     
,,iii4    ,,gas ,,light ,,machinery1    
,,at ,,the ,,royal ,,mint4    in        
,explanation of ,plate1 ,,ii4           
,accums1 ,discription of ,gas ,works4   
,illustration3 ,pl4 ,,iv4    ,accums1   
,description of ,gas ,works4    ,g4 ,h4 
,palmer1 ,del4    ,,gas ,,works4        

,westminster ,station                   
,illustration3 ,plate ,v4    ,accums1   
,description of ,gas ,works4      ,gas  
,holder at ,birmingham    without       
,specific ,gravity ,apparatus1          
capacity #cj1jjj ,cubic ,feet4    ,w4   
,read1 ,sculp4t      ,illustration3     
,plate ,,vi4    ,accums1 ,description of
 ,gas ,works4      ,gas ,holder at      
,chester    ,without ,specific ,gravity 
,apparatus1    ,capacity #cj1jjj ,cubic 
,feet4      ,gas ,holder at             
,westminster1    ,without ,specific     
,gravity ,apparatus1    ,capacity       
#ae1djj ,cubic ,feet    ,w4 ,read1      
,sculp4t      ,illustration3 ,accums1   
,description of ,gas ,works4    ,pl4    
,,vii4    ,,gas-,,works4    ,lowry1     
,del4t  ,sculp4t                        
,transcriber's ,notes                   
,inconsistent1 archaic and unusual      
language1 punctuation and spelling      
have been retained1 except as mentioned 
below4 ,the book uses a comma    for    
decimal point as well as for thousands  

separator4      ,the 7minor7 differences
 in wording between the ,table of       
,contents and    the actual text        
headings and the use of  7with or       
without full stop    and_/or space7 and 
l4 have not been standardised4          
,depending on the hard- and software    
used and their settings1 not all        
elements may display as intended4       
,when relevant1 texts have been removed 
from the plates and transcribed         
outside the plates4      ,plate ,,ii1   
',accums''3 as printed in original work4
      ,page xv1 entry ,,ammoniacal      
,,liquor3 there is no separate section  
for    this material1 but it is         
described in the first part of the      
section on    ,carbonate of ,ammonia on 
page #cjc4      ,page #dc1 ',pont       
,tops'3 possibly ,pontops4      ,page   
#di1 ',tramsaren1 near ,kidwelly'3      
possibly ,trimsaran4      ,page #gi1    
table3 the quantities given add up to   
#eef cubic feet4      ,page #hd1        
',enclosed are the result'3 as printed  

in the source document4      ,page #hf1 
,expenditure of ,process ,a3 the amounts
 given do not add up to    the total4   
,page #ajc_/ajd1 calculation3 the       
numbers given do not add up to the      
first sub-total4      ,page #aif1       
example of capacity calculation3 the    
dimensions given result    in a capacity
 of #bb1ejj cubic feet4      ,plate     
,,iii1 'discription'3 as printed in the 
source document4            ,changes3   
,footnotes have been moved to under the 
paragraph where they are    referenced4 
,tables printed over multiple pages have
 been re-combined into single    tables2
 where relevant1 items such as ,carried 
,over etc4 have been    removed4 ,the   
lay-out of the tables with financial    
analyses has been    standardised4      
,several obvious minor typographical and
 punctuation errors have been           
corrected silently4      ,page iii3 'as 
its little expresses' changed to 'as its
 title    expresses'4      ,page x3     
entries for pages #hj and #ha moved to  

their proper place4      ,page xv3 page 
number for entry ,,ammoniacal ,,liquor  
changed to #cjc 7see    above74         
,page #db1 'principle coal mines'       
changed to 'principal coal mines'4      
,page #dc3 ',cowpers ,main' changed to  
',cowper's ,main'4      ,page #adc3     
',melam' changed to ',malam'4      ,page
 #ahi1 'a fixed rigde point' changed to 
'a fixed ridge point'4      ,page #bah1 
'#aj1jj1jjj revolutions' changed to     
'#ajj1jjj revolutions'4      ,page #cjd3
 'it will turn blue litmus1 paper red'  
changed to 'it will    turn blue litmus 
paper1 red'4      ,page #cab3           
'sal-ammonia' changed to 'sal-ammoniac'4
      ,index3 ,lines used as ditto marks
 and the word 'ditto' have been         
replaced with the dittoed words and     
phrases4